PRACTICAL  MASONRY: 


OR 


A THEORETICAL  AND  OPERATIVE  TREATISE  OE  BUILDING ; 


CONTAINING  A 


SCIENTIFIC  ACCOUNT  OF  STONES,  CLAYS,  BRICKS,  MORTARS,  CEMENTS,  FIRE- 
PLACES, FURNACES,  &c.;  A DESCRIPTION  OF  THEIR  COMPONENT  PARTS, 
WITH  THE  MANNER  OF  PREPARING  AND  USING  THEM ; 

AND 


THE  FUNDAMENTAL  RULES  IN  GEOMETRY, 


ON 


M A S O N R Y A N p . S X 0 N E - C XI T T I;  N G ; ; • : • . 


WITH 


THEIR  APPLICATION  TO  PRACTICE  A C 


ILLUSTRATED  WITH  FORTY-FOUR  COPPERPLATE  ENGRAVINGS. 


By  EDWARD  SHAW,  Architect, 

AUTHOR  OP  “civil  ARCHITECTURE,**  “RURAL  ARCHITECTURE,**  ETC. 


\J 


BOSTON: 


PUBLISHED  BY  BENJAMIN  B.  MUSSEY. 

1846. 


Entered  according  to  Act  of  Congress,  in  the  year  1845,  by 
EDWARD  SHAW, 

in  the  Clerk’s  Office  of  the  District  Court  for  the  District  of  Massachusetts. 


CAMBRIDGE: 


METCALF  AND  COMPANY 

PHINTERS  TO  THE  CNIVERSITT. 


PREFACE. 


In  preparing  this  work  for  the  public,  it  has  been  the  design  of  the 
Compiler  to  avoid  prolixity,  by  the  rejection  of  such  things  as  are  already 
known  to  the  mechanic,  and  to  furnish  him  with  a knowledge  of  the  prin- 
ciples and  facts  on  which  he  might  be  supposed  to  require  information. 

Most  works  on  this  subject  set  out  with  a description  of  all  the  minutiae 
of  the  art  of  building ; and  though  they  may,  perhaps,  exhibit  something 
that  will  be  useful  to  the  apprentice,  yet  they  contain  much  that  is  of  no 
importance  to  the  practical  mechanic ; while  the  price  is  so  much  enhanced, 
that  few  can  well  afford  to  possess  them. 

As  permanency  in  building  seems,  at  the  present  day,  to  be  an  object 
more  desirable  than  formerly,  it  has  been  thought  that  a brief  account  of  the 
nature  and  qualities  of  building  materials,  with  a short  exposition  of  their 
component  parts,  would  not  be  misplaced  in  a treatise  of  this  kind.  The 
Compiler  flatters  himself,  that  he  has,  on  this  head,  furnished  some  informa- 
tion, that  will  be  serviceable  not  only  to  the  operator  but  to  the  proprietor ; 
neither  of  whom  can,  with  safety,  remain  unacquainted  with  the  quality  of 
the  materials  employed. 

The  best  writers  on  the  various  subjects  treated  of  in  this  work  have 
been  consulted,  and  such  use  made  of  their  labors,  by  abridging,  altering, 
abstracting,  and  condensing,  as  seemed  advisable  to  the  Compiler,  while  he 
has  added  much  that  has  been  the  result  of  many  years  of  practical  ex- 
perience and  personal  observation.  The  latest  improvements  in  building  have 
been  noticed  and  brought  to  the  attention  of  the  reader. 

In  short,  brevity  with  perspicuity,  and  utility  with  cheapness,  have  been 
aimed  at.  How  far  they  have  been  attained  is  submitted  to  the  decision  of 
an  enlightened  and  indulgent  public. 


/ S.  o / 


V 


I ■ 


I 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/detaiis/practicalmasonryOOshaw 


CONTENTS 


CHAPTER  I. 

SECTION  PAGE 

I.  Marble  ........  1 

II.  The  Polishing  of  Marble  . . . . . . .7 

III.  Artificial  Marble  .......  9 

IV.  The  Coloring  of  Marble  . . .....  9 

V.  Granite  .......  12 

VI.  Sienite  . . ■ • • • • • .21 

VII.  Greenstone  ........  23 

VIII.  Sandstone,  or  Freestone  . . . . . . .23 

IX.  Gneiss  ........  25 

X.  Mica-slate  . . . • • • • .26 

XI.  Slate  ........  26 

XII.  Soapstone,  or  Steatite  . . . • . . .29 

XIII.  Gypsum  . 30 

XIV.  Puzzolana  . . . • • • • .31 

XV.  Tras,  or  Terras  .......  32 

XVI.  Quarrying  . . . • • • • .32 

Table  showing  the  Weight  of  Granite  Stone  ....  37 

Mean  Weight  of  a Cubic  Foot  of  Stone  ....  38 

Table  of  Cylindrical  Measures  .....  38 

Table  for  the  Computation  of  the  Weight  of  Wrought  Iron  . . 39 

Rules  for  measuring  Hammered  Granite  Stone  . . .40 

CHAPTER  II. 

I.  Clay  . . . . . . . , .43 

II.  Brick-making  .......  44 

III.  Faced  or  Pressed  Bricks  . . . . . .47 

• 4 


VI 


CONTENTS. 


SECTION 

PAGE 

PI.ATE 

IV. 

Brick  Masonry  ...... 

48 

V. 

Tiles  . . ...... 

50 

VI. 

Compact  Limestone  ..... 

50 

VII. 

The  Burning  of  Lime  ...... 

51 

VIII. 

Of  Mortars  and  Cements  ..... 

52 

IX. 

Common  Mortar  and  Cement  ..... 

62 

X. 

Observations  on  Mortar  ..... 

63 

XI. 

Making  of  Mortar  ...... 

63 

XII. 

Monsieur  Loriat’s  Mortar  ..... 

64 

XIII. 

Dr.  Higgins  on  Mortar  ...... 

65 

XIV. 

Observations  on  Antique  Mortar  .... 

67 

XV. 

Stucco  ....... 

69 

XVI. 

Adam’s  Oil  Cement,  or  Stucco  .... 

69 

XVII. 

Scagliola  ....... 

71 

XVIII. 

Manner  of  forming  Columns  or  Pilasters  in  Scagliola 

71 

XIX. 

Modelling  for  Stucco  or  Plaster  of  Paris 

72 

XX. 

Moulding  of  Ornaments  ..... 

73 

XXI. 

Moulding  in  Plaster  ...... 

74 

XXII. 

Fixing  Ornaments  ...... 

74 

XXIII. 

Stucco  Cornices  ...... 

75 

XXIV. 

Circular  and  Elliptical  Cornices  or  Mouldings 

76 

XXV. 

External  Compositions  ...... 

76 

CHAPTER  III. 

PRACTICAL  GEOMETRY,  ADAPTED  TO  MASONRY  AND  STONE-CUTTING. 

I. 

On  the  Position  of  Lines  and  Points 

82 

1 

II. 

On  the  Species,  Nature,  and  Construction  of  Curve  Lines 

86 

2 

III. 

Of  the  Position  of  Lines  and  Planes,  and  the  Properties  arising 
from  their  Intersections  ..... 

89 

1 

IV. 

Of  the  Right  Sections  of  Arches  or  Vaults 

91 

3 

I. 

CHAPTER  IV. 

On  the  Nature  and  Construction  of  Trehedrals 

93 

2,  3 

II. 

On  the  Projection  of  a Straight  Line  bent  upon  a Cylindric  Sur- 
face, and  the  Method  of  drawing  a Tangent  to  such  a Projection 

97 

3. 

SECTION 

III. 

Application  of  Geometry  to  Planes  and  Elevations,  and  also  to  the 

PAGE 

PLATE 

Construction  of  Arches  and  Vaults  .... 

98 

4 

IV. 

On  the  Developments  of  the  Surfaces  of  Solids 

105 

4 

V. 

Construction  of  the  Moulds  for  Horizontal  Cylindretic  Vaults, 

either  terminating  Rightly  or  Obliquely,  upon  Plane  or  Cylin- 
drical Walls,  with  the  Joints  of  the  Courses  either  in  the  Di- 
rection of  the  Vault,  perpendicular  to  the  Faces,  or  in  Spiral 
Courses  .... 

106 

VI. 

On  Oblique  Arches  ..... 

109 

5-8,  10 

VII. 

A Circular  Arch  in  a Circular  Wall 

127 

9 

VIII. 

A Conic  Arch  in  a Cylindric  Wall  .... 

128 

9,  12 

IX. 

Construction  of  the  Moulds  for  Spherical  Niches,  both  with  Ra- 

diating and  Horizontal  Joints,  in  Straight  Walls  . 

132 

X. 

Examples  of  Niches  with  Radiating  Joints  in  Straight  Walls 

133 

13,  14 

XI. 

Examples  of  Niches  in  Straight  Walls,  with  Horizontal  Courses 

135 

14,  15 

XII. 

Construction  of  the  Moulds,  and  Formation  of  the  Stones,  for 

Domes  upon  Circular  Planes  .... 

137 

17,  18 

XIII. 

The  Manner  of  finding  the  Sections  of  Raking  Mouldings 

149 

19 

XIV. 

Construction  of  a Lintel,  or  an  Architrave,  in  three  or  more  Parts, 

over  an  Opening,  and  the  Steps  of  a Stair  over  an  Area 

150 

15,19,25 

XV. 

Construction  of  the  Stones  for  Gothic  Vaults,  in  Rectangular 

Compartments  upon  the  Plan  .... 

152  20,21,26 

CHAPTER  V. 


I. 

Ancient  Walls  ...... 

157 

22 

II. 

Construction  of  Brick  Arches  ..... 

159 

23 

III. 

Bricklaying  ...... 

159 

23 

IV. 

Foundations  ....... 

164 

23 

V. 

Walls,  &c.  ...... 

165 

23 

VI. 

The  Construction  of  Chimneys  .... 

166 

27 

VII. 

Fire-places  ...... 

168 

27,  28 

VIII. 

Warming  by  Steam  and  Hot  Water  .... 

169 

29-35 

IX. 

On  the  Construction  of  Ovens,  Boilers,  Fire-places,  and  of  the 
Setting  of  Copper  ..... 

177 

37,  38 

CONTENTS, 


viii 


CHAPTER  VI. 


ORDERS  OF  ARCHITECTURE. 


SECTION 

1.  Grecian  Doric 

. 

. 

. 

. 

PAGE 

. 181 

II.  Grecian  Ionic 

. 

. 

. 

181 

III.  Grecian  Corinthian 

. 182 

Glossary  of  Architectural  Terms  ....  183 


PLATE 

39,  40 
41,  42 
43,  44 


PRACTICAL  MASONRY. 


CHAPTER  I. 

SECTION  I.  — Marble. 

The  class  of  stones  denominated  Calcareous  is  exceedingly  numerous  and 
abundant  in  nature.  Of  these,  marble  is  the  most  important.  It  is  a granular 
carbonate  of  lime,  or  a compact  limestone,  varying  in  color,  texture,  and  hard- 
ness. Its  structure  is  both  foliated  and  granular.  The  grains  are  of  various 
sizes,  from  coarse  to  very  fine,  sometimes,  indeed,  so  fine  that  the  mass  appears 
almost  compact.  When  these  grains  are  white,  and  of  a moderate  size,  this 
mineral  strongly  resembles  white  sugar  in  solid  masses. 

Its  fracture  is  foliated ; but  the  faces  of  the  laminae,  which  vary  in  extent, 
according  to  the  size  of  the  grains,  are  sometimes  distinguishable  only  by  their 
glimmering  lustre.  When  the  structure  is  very  finely  granular,  the  fracture  often 
becomes  a little  splintery. 

Both  its  hardness  and  the  cohesion  of  its  grains  are  somewhat  variable.  In 
some  cases,  its  hardness  undoubtedly  depends  on  the  presence  of  siliceous 
particles ; indeed,  it  sometimes  gives  a few  sparks  with  steel.  Its  specific  gravity 
usually  lies  between  2.71  and  2.84,  water  being  1.  That  is,  water  as  a 
standard  being  taken  as  a unit,  the  specific  gravity  of  marble  is  from  2iVo  units 
to  2tVo  units  when  compared  to  water,  or  about  2f  times  greater. 

It  is  more  or  less  translucent,  but,  in  the  dark  colored  varieties,  at  the  edges 
only.  Its  color  is  most  commonly  white  or  gray,  often  snow-white,  and  some- 
times grayish -black.  It  also  presents  certain  shades  of  blue,  green,  red,  or 
yellow.  Most  frequently  the  colors  are  uniform,  but  sometimes  variegated  in 
spots,  veins,  or  clouds,  arising  from  the  intermixture  of  foreign  substances. 

Marble  is  essentially  a carbonate  of  lime,  which  is  composed  of  57  parts  of 
lime  and  43  parts  of  carbonic  acid ; a little  water  is  usually  present.  It  is  soluble 
in  nitric  acid ; and,  by  the  escape  of  carbonic  acid,  more  or  less  effervescence  is 

1 


2 


PRACTICAL  MASONRY 


produced  ; some  varieties,  however,  effervesce  very  slowly.  Before  the  blow-pipe 
it  decrepitates,  and,  if  pure  carbonate  of  lime,  it  is  perfectly  infusible  ; but  by  a 
strong  heat  its  carbonic  acid  is  driven  off,  and  quicklime,  or  pure  lime,  whose 
taste  is  well  known,  remains. 

Marble,  in  the  strict  propriety  of  the  term,  should  be  confined  to  those  varieties 
of  carbonate  of  lime  which  are  susceptible  of  a polish  ; including  also  some 
minerals,  in  which  carbonate  of  lime  abounds.  But  among  artists  this  term  is 
sometimes  extended  to  serpentine,  basalt,  See.,  when  polished. 

Both  granular  and  compact  limestone  furnish  numerous  varieties  of  marble ; 
but  those  which  belong  to  the  former  exhibit  a more  uniform  color,  are  generally 
susceptible  of  a higher  polish,  and  are  hence  most  esteemed  for  statuary  and 
some  other  purposes.  The  uniformity  of  color,  so  common  in  primitive  marbles, 
is  sometimes  interrupted  by  spots,  or  veins,  or  clouds,  of  different  colors,  arising 
from  the  intermixture  of  hornblende,  serpentine,  &,c.  Among  the  foreign  marbles 
we  may  mention  : — 

The  Carrara  Marble.  Found  at  Carrara,  in  Tuscany.  It  was  highly  esteem- 
ed by  the  ancients,  and  is  at  present  more  employed  by  the  Italian  artist  than 
any  other  kind  for  statuary,  vases,  slabs  for  household  furniture,  &.c.  It  is  very 
white,  sometimes  veined  with  gray,  and  has  a grain  considerably  fine.  In  the 
centre  of  the  blocks  of  this  marble  very  limpid  rock-crystals  are  found,  which  are 
called  Carrara  diamonds.  The  average  price  of  this  marble  is  ten  or  twelve  dol- 
lars a cubic  foot. 

The  Liini  Marble,  found  also  in  Tuscany,  is  extremely  white,  and  its  grain 
is  a little  finer  than  that  of  Carrara.  Of  this  marble,  it  is  generally  supposed,  the 
famous  Apollo  Belvidere,  in  the  Vatican  at  Rome,  is  made,  as  well  as  the  Antin- 
oiis  of  the  Capitol,  and  the  Antinoiis  in  bas-relief  in  the  Napoleon  Museum. 

The  Parian  JMarble,  obtained  from  the  islands  of  Paros,  Naxos,  &.C.,  in  the 
Archipelago,  was  much  employed  by  the  ancients.  It  is  white,  but  often  with  a 
slight  tinge  of  yellow.  Its  grains  are  larger  than  those  of  the  Carrara  marble. 
The  celebrated  Venus  de  Medicis,  in  the  gallery  at  Florence,  is  of  this  marble. 
It  was  called  by  the  ancients  Lychnites,  in  consequence  of  its  quaraies  being  of- 
ten worked  by  the  light  of  a lamp.  It  is  on  Parian  marble  that  the  celebrated  ta- 
bles at  Oxford  are  inscribed. 

The  Pentelic  Marble.  From  Mount  Penteles,  near  Athens.  This  marble 
much  resembles  the  preceding,  but  is  more  dense  and  fine-grained ; it  sometimes 
exhibits  faint  greenish  zones,  produced  by  greenish  talc,  whence  the  Italian 
name  Cipilino  Statiiario.  The  principal  monuments  of  Athens  were  of  Pentelic 
marble,  such  as  the  Parthenon,  the  Propylaea,  and  the  Hippodrome.  Among  the 
statues  of  this  marble  in  the  Napoleon  Museum,  at  Paris,  are  the  Torso;  a 


OF  MARBLE. 


3 


Bacchus  in  repose  ; a Jason  (called  Cincinnatus)  ; a Paris  ; the  Discobolus  reposing  ; 
the  bas-relief  known  by  the  name  of  the  Sacrifice ; the  Throne  of  Satui-n ; 
the  Tripod  of  Apollo;  and  the  two  beautiful  Athenian  inscriptions  known  by  the 
name  of  “Xointel  Marbles,”  because  M.  Xointel  caused  them  to  be  brought  from 
Athens  to  Paris  in  1672. 

Greek  JVhite  .Marble.  The  marble  to  which  the  statuaries  of  Rome  give  the 
name  of  .Marino  Greco  is  of  a very  bright  snow-white  color,  close  and  fine- 
grained, and  of  a hardness  which  is  rather  superior  to  that  of  other  white  mar- 
bles. It  takes  a very  fine  polish.  It  has  been  called  Corallic  marble,  from  being 
found  near  the  river  Coralus,  in  Phrygia.  According  to  Pliny,  it  was  found  in 
Asia,  in  masses  of  small  dimensions ; and  it  is  said  that  a similar  kind  occurs  On 
Mount  Canuto,  near  Palermo,  in  Sicily.  The  Greek  marble  was  obtained  from 
several  islands  in  the  Archipelago ; such  as  Scio,  Samos,  &ic.  Among  the 
statues  of  this  marble  in  the  Napoleon  Museum  are  a Bacchus,  and  Zeno,  the 
philosopher. 

Translucid  Jfliite  .Marble.  This  much  resembles  Pai-ian  marble,  but  differs 
from  it  as  being  more  translucid.  There  are,  at  Venice,  and  several  other  towns 
in  Lombardy,  columns  and  altars  of  this  marble,  tbe  quarries  of  which  are 
perfectly  unknown. 

Flexible  JVhite  .Marble.  It  is  of  a beautiful  white  color,  and  fine  grain. 
There  are  five  or  six  tables  of  it  preserved  in  the  house  of  the  Prince  Borghese, 
at  Rome.  They  were  dug  up,  as  the  Abbe  Fortis  was  told,  in  the  field  of 
Mondragone.  Being  set  on  end  they  bend,  oscillating  backward  and  forward  ; 
when  laid  horizontally,  they  form  a curve. 

JJliite  .Marble  of  .Mount  llymettus.  This  is  not  a very  pure  white  variety,  but 
inclines  a little  to  gray.  Pliny  informs  us  that  Lucius  Crassus,  the  orator,  was 
exposed  to  the  sarcasms  of  Marcus  Brutus,  because  he  had  adorned  his  house 
with  six  columns,  twelve  feet  high,  of  the  Ilymettian  marble.  The  statue  of 
Meleager,  in  the  Napoleon  Museum,  is  of  this  marble. 

These  are  the  chief  white  marbles  which  the  ancients  used  for  the  purposes 
of  architecture  and  sculpture. 

Black  ^intique  .Marble.  (jYero  .Intico  of  the  Italians.)  This  differs  from  the 
modern  black  marbles  by  the  superior  intensity  of  its  color.  It  has  been  said 
that  the  ancients  procured  this  marble  from  Greece,  but  it  has  been  ascertained 
that  quarries  of  real  antique  black  marble  have  been  rediscovered,  which  were 
wrought  by  the  ancients,  and  of  which  the  remains  are  still  to  be  seen,  at  the 
distance  of  two  leagues  from  Spa,  towards  Franchimont,  not  far  from  Aix-la- 
Chapelle.  This  marble  is  extremely  scarce,  and  occurs  only  in  wrought  pieces. 

Red  .inti que  .Marble.  {Rosso  .intico  oi  the  Italians.)  This  beautiful  marble 


4 


PRACTICAL  MASONRY. 


is  of  a deep  blood-red  color,  here  and  there  with  white  veins,  and,  if  closely 
examined,  is  found  to  be  sprinkled  over  with  minute  white  dots,  as  if  it  were 
strewed  sand.  Of  this  kind  is  the  Egyptian  Antinoiis,  in  the  museum  at  Paris. 
But  the  most  esteemed  variety  of  Rosso  Antico  is  that  of  a very  deep  red, 
without  any  veins,  such  as  it  is  seen  in  the  two  antique  chairs,  and  in  the  bust  of 
an  Indian  Bacchus  in  the  same  museum.  The  white  spots,  or  points,  which  are 
never  wanting  in  the  true  red  antique,  distinguish  it  from  others  of  the  same 
color.  It  is  not  known  from  wdience  the  ancients  obtained  this  marble ; the 
conjecture  is  that  it  was  brought  from  Egypt.  There  is,  in  the  Grimani  Palace, 
at  Venice,  a colossal  statue  of  Marcus  Agrippa,  in  Rosso  Antico,  \vhich  w'as 
formerly  preserved  in  the  Pantheon,  at  Rome. 

Green  Antique  Marble.  (The  Verde  Antico  of  the  Italians.)  This  may  be 
considered  a kind  of  breccia,  the  paste  of  which  is  a mixture  of  talc  and  lime- 
stone; and  the  dark  green  fragments  are  owing  to  serpentine  more  or  less 
pure.  The  Verde  x\ntico  of  the  best  quality  is  that  of  which  the  paste  is  of  a 
grass-green,  and  the  blackish  spots  are  of  that  variety  of  serpentine  which  is 
called  noble  serpentine.  This  marble  is  much  esteemed  in  commerce,  but  Icirge 
pieces  of  a fine  quality  are  seldom  seen.  There  are  four  fine  columns  of  it 
in  the  Napoleon  Museum ; but  much  more  beautiful  ones  sre  preserved  at 
Parma.  This  Verde  Antico  must  not  be  confounded  with  the  marbles  known 
by  the  names  of  Vert-de-mer  or  Vert -d’ Egypt.  The  real  Verde  Antico  is  a 

breccia,  and  is  never  mingled  with  red  spots,  w'hile  those  just  mentioned  are 
veined  marbles,  mixed  with  a dull  red  substance,  which  gives  them  a brownish 
hue. 

Red-spotted  Green  Antique  Marble.  Its  ground  is  very  dark  green,  here 
and  there  marked  with  small  red  and  black  spots.  The  quarries  of  this  mar- 
ble are  lost,  and  it  is  found  only  in  small  pieces,  which  are  made  into 
tablets,  &c. 

Leek  Marble.  (Marbre  Poireau  of  the  French  lapidaries.)  This  is  a mix- 
ture of  limestone  and  a talcose  substance  of  light  green,  shaded  with  blackish- 
green,  and  related  to  serpentine.  Its  texture  is  filamentose,  and,  as  it  w^ere, 
ligneous;  its  fragments  are  splintery.  When  polished  it  exhibits  long  green 
veins.  Like  all  other  talcose  marbles,  it  soon  decomposes  in  the  open  air. 
There  is  a table  of  it  in  the  Plotel  de  la  Monnoie,  at  Paris.  Its  quarries  are  lost. 

Marble  Petit  Antique,  of  the  French  lapidaries.  It  is  traversed  wfith 
white  and  gray  veins,  the  two  colors  being  disposed  in  uninterrupted  threads ; 
the  tables  made  of  this  marble  are  irregularly  striped  their  whole  length,  which 
has  a very  fine  effect.  It  is  much  esteemed,  and  only  made  use  of  for 
inlaying  ornamental  furniture.  Its  quanies  are  unknown. 


OF  MARBLE. 


S 

Yellow  Antique  Marble.  (Giallo  Antico  of  the  Italians.)  Of  this  there 
are  three  varieties.  The  first  has  more  or  less  the  color  of  the  yolk  of  an 
egg,  and  is  nearly  of  an  uniform  tint ; the  other  is  marked  with  black  or  deep 
yellow  rings,  and  the  last  is  merely  a paler  colored  variety  of  the  first.  These 
different  marbles,  for  which  the  Sienna  marble  is  a good  substitute,  are  found 
only  in  small  detached  pieces,  and  in  antique  inlaid  work.  It  is  in  this  manner 
that  the  two  tables  of  lazulite  in  the  Napoleon  Museum  are  surrounded  with 
a border  of  the  deep  yellow  variety. 

Grand  Antique  Marble.  This  variety,  which  is  a breccia,  containing  some 
shells,  consists  of  large  fragments  of  a black  marble  united  by  veins,  or  lines, 
of  shining  white.  This  superb  marble,  the  quarries  of  which  are  lost,  is 
sometimes  found  in  detached  pieces  and  wrought.  There  are  four  columns 
of  it  in  the  museum  at  Paris.  A less  valuable  variety  is  that  in  which  the 
spots,  instead  of  being  an  entire  intense  black,  are  of  a gray  color. 

Antique  CipoHn  Marble.  Cipolin  is  a name  given  to  all  such  marbles  as 
have  greenish  zones,  caused  by  green  talc ; their  fracture  is  granular  and 
shining,  and  shows  here  and  there  plates  of  talc.  They  are  never  found  to 
contain  marine  bodies.  The  ancients  have  made  frequent  use  of  cipolin.  It 
takes  a fine  polish,  but  its  ribbon-like  stripes  always  remain  dull,  and  are  that 
part  of  the  marble  which  first  decomposes,  when  exposed  to  the  open  air. 
There  are  modern  cipolins  as  fine  as  that  used  by  the  ancients. 

Purple  Antique  Breccia  Marble.  This  should  not  be  confounded  with 
African  breccia.  There  is,  perhaps,  no  marble,  the  color  and  spots  of  which 
are  so  variable  as  that  of  the  violet  breccia.  The  following  are  the  chief 
varieties.  The  first  is  that  from  which  the  name  of  the  marble  is  derived; 
it  has  a purplish-brown  base,  in  which  are  imbedded  large  angular  fragments 
of  a light  purple  color,  and  others  of  a white  color.  This  first  variety  can  be 
employed  only  in  large  works,  on  account  of  the  size  of  its  spots,  which  are 
sometimes  a foot  in  diameter.  There  is  a beautiful  table  of  it  in  the  Napoleon 
Museum.  The  second  variety  is,  as  it  were,  the  miniature  of  the  first ; it 
exhibits  the  same  spots,  but  within  a much  narrower  compass,  so  that  it  may 
be  used  for  less  gigantic  works  than  those  for  which  the  other  is  employed. 
The  third  variety  is  known  in  commerce  by  the  name  of  rose-colored  marble; 
in  this,  the  spots,  instead  of  being  white  and  light  purple,  have  a pleasing  rose- 
color.  It  is  scarce  and  never  seen  in  large  pieces.  The  fourth,  which  is  the 

[The  term  breccia,  which  has  often  been  used  In  the  preceding  pages,  is  applied  to  an  aggregate,  composed 
of  angular  fragments  of  the  same  or  different  minerals,  united  by  some  cement ; sometimes,  however,  a few 
of  the  fragments  are  a little  rounded.  The  different  fragments  always  present  a variety  of  colors.  There 
are  several  varieties,  some  of  which  are  susceptible  of  a fine  polish.] 


6 


PRACTICAL  MASONRY. 


most  beautiful,  appears,  at  first  view,  to  be  perfectly  distinct  from  the  others, 
but  it  is,  nevertheless,  a mere  variety  of  the  purple  breccia.  Its  ground  is  of 
a yellowish -green  color,  and  the  spots,  which  are  of  various  sizes,  are  white, 
green,  purplish,  and  yellow,  mottled  with  red ; these  various  spots  are  traversed  by 
straight  lines  of  grayish -white  color.  This  fourth  variety  is  very  scarce.  There 
are,  however,  two  tables  of  it  at  Paris,  in  the  possession  of  private  individuals. 

Jlfrican  Breccia  Marble.  Its  ground  is  black,  variegated  with  large  fragments 
of  a grayish-white,  of  a deep  red,  or  of  a purplish  wine-color;  but  these  latter 
are  always  smaller  than  the  former.  This  is  one  of  the  most  beautiful  marbles 
existing,  and  has  a supurb  effect  when  accompanied  by  gilt  ornaments.  Though 
rather  less  vivid  in  its  colors  than  the  preceding  violet  breccia,  it  is  yet,  on  the 
whole,  more  beautiful.  Whether  Africa  is  the  part  of  the  world  where  it  is 
found,  as  its  name  implies,  is  not  certain.  The  pedestal  of  Venus  leaving  the 
Bath,  and  a large  column,  both  in  the  Napoleon  Museum,  are  of  this  marble. 

There  are  other  varieties  of  breccia  marble,  not  differing  materially  from  those 
already  described  ; they  are,  many  of  them,  very  beautiful,  but  very  scarce,  found 
only  in  small  pieces  among  the  ruins  at  Rome. 

Marbles  are  found  abundantly,  and  in  variety,  in  all  countries.  There  are  many 
curious  varieties  in  the  United  States.  The  chief  quarries  that  have  been  noticed 
are  the  following : — 

Slockbridge  and  Lanesboroiigfi  Marble.  In  Berkshire  county,  Massachusetts. 
Its  grain  is  somewhat  coarse,  and  its  color  white,  sometimes  with  a slight  tinge  of 
blue.  A quarry  has  also  been  opened  of  a similar  kind  of  marble,  at  Pittsfield, 
in  the  same  county. 

Vermont  Marble.  It  is  found  of  various  qualities,  according  to  Professor 
Hall,  in  many  places  on  the  west  side  of  the  Green  Mountains.  A few  years 
since,  a valuable  quarry  was  found  in  Middlebury,  on  Otter  Creek,  eleven  miles 
above  Vergennes.  The  quarry  forms  one  bank  of  the  creek  for  several  roods, 
and  extends  back  into  the  side  of  a hill,  to  a distance  at  present  unknown. 
The  stone  lies  in  irregular  strata,  varying  considerably  in  thickness,  but  all  more 
or  less  inclined  to  the  northwest.  The  marble  is  of  different  colors  in 
different  parts  of  the  bed.  On  one  side  it  is  of  a pure  white,  and  of  a quality, 
if  at  all,  but  little  inferior  to  the  Italian  marble ; but  this  seems  to  constitute  but 
a small  portion  of  the  whole  mass.  The  color  that  predominates  through  most 
parts  of  the  quairy  is  a gray  of  different  intensities.  The  marble  of  both  kinds 
is  solid,  compact,  free  from  veins  of  quartz,  and  susceptible  of  an  excellent  polish. 
A mill  of  peculiar  construction  has  been  erected  for  the  purpose  of  sawing  the 
stone  into  slabs.  It  contains  sixty-five  saws,  which  are  kept  almost  in  continual 
operation.  During  the  years  of  1809  and  1810  these  saws  cut  out  20,000  feet 


OF  M A E B L E . 


7 


of  slabs,  and  the  sales  of  marble  tables,  side-boards,  tomb-stones,  &c.,  in  the  same 
period,  amounted  to  about  11,000  dollars. 

Some  of  the  Vermont  marbles  are  as  white  as  the  Carrara  marble,  with  a grain 
intermediate  betwen  that  of  the  Carrara  and  Parian  marbles. 

S\'ew  Haven  Marble.  The  texture  of  this  very  beautiful  marble  is  granular, 
but  very  fine.  Its  predominant  colors  are  gray  and  blue,  richly  variegated  by  veins 
or  clouds  of  white,  black,  or  green ; indeed,  the  green  often  pervades  a large 
mass.  It  takes  a high  polish,  and  endures  the  action  of  fire  remarkably  well. 
This  marble  contains  chromate  of  iron,  magnetic  oxide  of  iron,  and  serpentine  ; 
hence  it  resembles  the  Vert  Hntique,  and  is,  perhaps,  the  only  marble  of  the  kind 
hitherto  discovered  in  America. 

Thomaston  Marble.  From  Lincoln  county,  Maine.  It  is,  in  general,  fine- 
grained, and  its  colors  are  often  richly  variegated.  Sometimes  it  is  white,  or 
grayish-white,  diversified  with  veins  of  a dili’erent  color.  But,  in  the  finest  pieces, 
the  predominant  color  is  gray,  or  bluish-gray,  interrupted  with  whitish  clouds, 
which,  at  a small  distance,  resemble  the  minutely  shaded  parts  of  an  engraving, 
and,  at  the  same  time,  traversed  by  innumerable  stnall  and  irregular  veins  of  black 
and  white.  It  receives  a fine  polish,  and  is  well  fitted  for  ornamental  works. 

Some  of  the  white  marble  of  A'ermont,  and  that  which  may  be  obtained  at 
Smithli.  id,  in  Rhode  Island,  more  peculiarly  deserve  the  name  of  statuary  marble. 

Flcj'ible  Marble  has  been  observed  at  Pittsford,  Rutland  county,  Vermont ; 
and  at  Pittsfield,  in  Massachusetts. 

Pennsylvania  Marble.  There  is  found  at  Aaronsburg,  in  Northumberland 
county,  a black  marble.  It  is  of  compact  limestone,  containing  white  specks. 
At  Marbletown,  near  the  Hudson  River,  in  the  State  of  New  York,  is  a quany  of 
very  fine  black  marble,  spotted  with  white  shells.  Marble  has  also  been  found  in 
Virginia,  and  some  other  of  the  United  States.  But  the  state  of  the  arts  has  not, 
hitherto,  directed  the  attention  of  the  curious  so  much  to  this  subject  as  it  intrin- 
sically deserves. 


SECTION  II. — The  Polishing  of  Marble. 

The  art  of  cutting  and  polishing  marble  was,  of  course,  known  to  the  ancients, 
whose  mode  of  proceeding  appears  to  have  been  nearly  the  same  with  that 
employed  at  present ; except,  perhaps,  that  they  were  unacquainted  with  those 
superior  mechanical  means,  which  now  greatly  facilitate  the  labor,  and  diminish 
the  expense  of  the  articles  thus  produced.  There  are  many  manufactories  of 
this  kind,  generally  called  marble-mills,  on  the  continent,  and  also  in  Great  Britain  ; 


8 


PRACTICAL  MASONRY. 


but  as  the  principle  on  which  they  proceed  is  nearly  the  same  in  all,  it  will  suffice 
in  this  place  to  give  the  description  of  one  or  two  of  the  latter. 

An  essential  part  of  the  art  of  polishing  marble  is  the  choice  of  substances  by 
which  the  prominent  parts  are  to  be  removed.  The  first  substance  should  be  the 
sharpest  sand,  so  as  to  cut  as  fast  as  possible,  and  this  is  to  be  used  till  the  surface 
becomes  perfectly  flat.  After  this,  the  surface  is  rubbed  with  a finer  sand,  and 
frequently  with  a third.  The  next  substance,  after  the  finest  sand,  is  emery,  of 
difierent  degrees  of  fineness.  This  is  followed  by  the  red  powder  called  tripoli, 
which  owes  its  cutting  quality  to  the  oxide  of  iron  it  contains.  Common  iron- 
stone, powdered  and  levigated,  answers  the  purpose  very  well.  This  last 
substance  gives  a tolerably  fine  polish.  This,  however,  is  not  deemed  sufficient. 
The  last  polish  is  given  with  putty.  After  the  first  process,  which  merely  takes 
away  the  inequalities  of  the  surface,  the  sand  employed  in  preparing  it  for  the 
emery  should  be  chosen  of  an  uniform  quality.  If  it  abounds  with  some  particles 
harder  than  the  rest,  the  surface  will  be  liable  to  be  scratched  so  deep  as  not  to 
be  removed  by  the  emery.  In  order  to  get  the  sand  of  uniform  quality,  it  should 
be  levigated  and  washed.  The  hard  particles  being  generally  of  a different 
specific  gravity  to  the  rest,  may,  by  this  means,  be  separated.  This  method  will 
be  found  much  superior  to  that  of  sifting.  The  substance  by  which  the  sand 
is  rubbed  upon  the  marble  is  generally  an  iron  plate,  especially  for  the  first 
process.  A plate  of  an  alloy  of  lead  and  tin  is  better  for  the  succeeding 
processes,  with  the  fine  sand  and  emery.  The  rubbers  used  for  the  polishing,  or 
last  process,  consist  of  coarse  linen  cloths,  such  as  hop- bagging,  wedged  tight 
into  an  iron  plane.  In  all  of  these  processes,  a constant  supply  of  water,  in  small 
quantities,  is  absolutely  necessary. 

The  sawing  of  marble  is  performed  on  the  same  principles  as  the  first  process 
of  polishing.  The  saw  is  of  soft  iron,  and  is  continually  supplied  with  w'ater  and 
the  sharpest  sand. 

Marble  is  extensively  used  for  building,  statuary,  decorations,  and  inscriptions. 
In  warm  countries  it  is  one  of  the  most  durable  of  substances,  as  is  proved  by 
the  edifices  of  Athens,  which  have  retained  their  polish  for  more  than  two 
thousand  years.  Severe  frost,  preceded  by  moisture,  causes  it  to  crack  and  scale; 
great  heat  reduces  it  to  quicklime.  It  may  be  burnt,  like  other  varieties  of  lime- 
stone, into  lime  for  preparing  mortar,  or  employed  as  a flux  for  certain  ores, 
particularly  those  which  contain  alumine  and  silex. 

White  marble  is  sometimes  cleaned  by  muriatic  acid  diluted  with  water.  Spots 
of  oil  stain  white  marble,  so  that  they  cannot  be  taken  out. 


OF  MARBLE. 


9 


SECTION  III.  — Artificial  Marble. 


The  stucco,  whereof  they  make  statues,  busts,  basso-relievos,  and  other 
ornaments  of  architecture,  ought  to  be  marble  pulverized,  mixed  in  a certain 
proportion  with  plaster;  the  whole  well  sifted,  worked  up  with  water,  and  used 
like  common  plaster.  (See  Stucco.) 

There  is  also  a kind  of  artificial  marble,  made  of  flake  selenites,  or  a trans- 
parent stone  resembling  the  plaster,  which  becomes  very  hard  and  receives  a 
tolerable  polish,  and  may  deceive  the  eye.  This  kind  of  selenites  resembles 
Muscovy  talc.  There  is  another  sort  of  artificial  marble,  formed  by  corrosive 
tincture,  which,  penetrating  into  white  marble,  to  the  depth  of  a line  or  more, 
imitates  the  various  colors  of  other  dearer  marbles.  There  is  also  a preparation 
of  brimstone  in  imitation  of  marble.  To  do  this  you  must  provide  yourself  with 
a flat  and  smooth  piece  of  marble.  On  this  make  a border  or  wall,  to  encompass 
either  a square  or  oval  table,  which  may  be  done  either  with  wax  or  clay.  Then, 
having  provided  several  sorts  of  colors,  as  white  lead,  vermilion,  lake,  orpiment, 
massicot,  Prussian-blue,  &cc.,  melt,  on  a slow  fire,  some  brimstone,  in  several 
glazed  pipkins  ; put  one  particular  sort  of  color  into  each,  and  stir  it  well  together; 
then,  having  before  oiled  the  marble  all  over  within  the  wall,  with  one  color  quickly 
drop  spots  upon  it  of  larger  and  less  size ; after  this  take  another  color,  and  do 
as  before ; and  so  on,  till  the  stone  is  covered  with  spots  of  all  the  colors  you 
design  to  use.  When  this  is  done,  you  are  next  to  consider  what  color  the  mass 
or  ground  of  your  table  is  to  be ; if  of  a gray  color,  then  take  fine  sifted  ashes, 
and  mix  them  up  with  melted  brimstone,  or  if  red,  with  English  red  ochre;  if 
white,  with  white  lead;  if  black,  with  lamp  or  ivory  black.  Your  brimstone  for 
the  ground  must  be  pretty  hot,  that  the  colored  drops  on  the  stone  may  unite  and 
incorporate  with  it.  When  the  ground  is  poured  even  all  over,  you  are  next,  if 
judged  necessary,  to  put  a thin  wainscot  board  upon  it ; this  must  be  done  while 
the  brimstone  is  hot,  making  also  the  board  hot,  which  ought  to  be  thoroughly 
dry,  in  order  to  cause  the  brimstone  to  stick  the  better  to  it.  When  the  whole  is 
cold,  take  it  up,  and  polish  it  with  a cloth  and  oil,  and  it  will  look  very  beautiful. 


Iv A S' 


SECTION  IV.  — The  Coloring  of  Marble. 

The  coloring  of  marble  is  a nice  art,  and,  in  order  to  succeed  in  it,  the  pieces 
of  marble  on  which  the  experiments  are  tried  must  be  well  polished,  and  clear 

2 


10 


PRACTICAL  MASONRY. 


from  the  least  spot  or  vein.  The  harder  the  marble  is,  the  better  it  will  be,  and 
the  greater  the  heat  necessary  in  the  operation  ; therefore,  alabaster,  and  the 
common  soft  white  marble,  are  very  improper  to  perform  these  operations  upon. 

Heat  is  always  necessary,  for  the  opening  of  the  pores,  so  as  to  render  it  fit  to 
receive  the  colors ; but  the  marble  must  never  be  made  red-hot,  for  then  the 
texture  of  the  marble  itself  is  injured,  and  the  colors  are  burnt,  and  lose  their 
beauty.  Too  small  a degree  of  heat  is  as  bad  as  too  great ; for,  in  this  case, 
though  the  marble  receives  the  color,  it  will  not  be  fixed  in  it,  nor  strike  deep 
enough.  Some  colors  will  strike  even  cold ; but  they  are  never  so  well  sunk  in 
as  when  a just  degree  of  heat  is  used.  The  proper  degree  is  that,  which, 
without  making  the  marble  red,  will  make  the  liquor  boil  on  its  surface.  The 
menstruums  used  to  strike  in  the  colors  must  be  varied  according  to  the  nature 
of  the  color  to  be  used.  A lixivium  made  of  horse’s  or  dog’s  urine,  with  four 
parts  of  quicklime,  and  one  part  pot-ashes,  is  excellent  for  some  colors ; common 
lye  of  wood-ashes  does  very  well  for  others;  for  some,  spirit  of  wine  is  best; 
and  finall}^  for  others,  oily  liquors,  or  common  white  wine. 

The  colors  which  have  been  found  to  succeed  best  with  the  peculiar  menstru- 
ums, are  these : stone-blue  dissolved  in  six  times  the  quantity  of  spirit  of  wine, 
or  of  the  urinous  lixivium,  and  that  color  which  the  painters  call  litmus  dissolved 
in  common  lye  of  wood-ashes.  An  extract  of  saffron,  and  that  color  made  of 
buckthorn  berries,  and  called  by  the  painters  soap-green,  both  succeed  well  dis- 
solved in  urine  and  quicklime,  and  tolerably  well  in  spirit  of  wine.  Vermilion,  and 
a fine  powder  of  cochineal,  succeed  also  very  well  in  the  same  liquors.  Dragon’s- 
blood  succeeds  very  well  in  spirit  of  wine,  as  does  also  a tincture  of  logwood  in 
the  same  spirit.  Alkanet-root  gives  a fine  color,  but  the  only  menstruum  to  be 
used  for  this  is  oil  of  turpentine  ; for  neither  spirit  of  wine,  nor  any  lixivium,  will 
do  with  it.  There  is  a kind  of  substance  called  dragon’s-blood-in-tears,  which, 
mixed  with  urine  alone,  gives  a very  elegant  color. 

Besides  these  mixtures  of  colors  and  menstruums,  there  are  some  colors  which 
are  to  be  laid  on  dry  and  unmixed.  These  are  dragon’s-blood  of  the  purest 
kind,  for  a red ; gamboge,  for  a yellow ; green  wax,  for  a green  ; common  brim- 
stone, pitch,  and  turpentine,  for  a brown  color.  The  marble,  for  these  experi- 
ments, must  be  made  considerably  hot,  and  the  colors  are  to  be  rubbed  on  dry, 
in  the  lump.  Some  of  these  colors,  when  once  given,  remain  immutable ; others 
are  easily  changed  or  destroyed.  Thus  the  red  color,  given  by  dragon’s-blood, 
or  by  the  decoction  of  logwood,  will  be  wholly  taken  away  by  oil  of  tartar,  and 
the  polish  of  the  marble  not  hurt  by  it. 

A fine  gold  color  is  given  in  the  following  manner:  take  crude  sal-ammoniac. 


OF  MARBLE. 


11 


vitriol,  and  verdigris,  of  each  equal  quantities ; "white  vitriol  succeeds  best,  and 
all  must  be  thoroughly  mixed  in  fine  powder. 

The  staining  of  marble,  to  all  degrees  of  red  or  yellow,  by  solution  of  dragon’s- 
blood  or  gamboge,  may  be  done  by  reducing  these  gums  to  powder,  and  grinding 
them  with  the  spirit  of  wine,  in  a glass  mortar;  but  for  smaller  attempts,  no 
method  is  so  good  as  the  mixing  a little  of  either  of  these  powders  with  spirit 
of  wine,  in  a silver  spoon,  and  holding  it  over  burning  charcoal.  By  this  means, 
a fine  tincture  will  be  extracted,  and,  with  a pencil  dipped  in  this,  the  finest  traces 
may  be  made  on  the  marble,  while  cold,  which,  on  heating  of  it  afterwards,  either 
on  sand  or  in  a baker’s  oven,  will  all  sink  very  deep,  and  remain  perfectly  distinct 
in  the  stone.  It  is  very  easy  to  make  the  ground-color  of  the  marble  red  or 
yellow,  by  this  means,  and  leave  white  veins  in  it.  This  is  to  be  done  by  covering 
the  places  where  the  whiteness  is  to  remain  with  some  white  paint,  or  even  with  two 
or  three  doubles  only  of  paper,  either  of  which  will  prevent  the  color  from  pene- 
trating in  that  part.  All  the  degrees  of  red  are  to  be  given  to  the  marble  by  the 
means  of  this  gum  alone ; a slight  tincture  of  it,  without  the  assistance  of  heat 
to  the  marble,  gives  only  a pale  fleshcolor;  but  the  stronger  tinctures  give  it  yet 
deeper.  To  this  the  assistance  of  heat  adds  yet  greatly  ; and  finally,  the  addition 
of  a little  pitch  to  the  tincture  gives  it  a tendency  to  blackness,  or  any  degree 
of  deep  red  that  is  desired. 

A blue  color  may  be  given  to  marble,  by  dissolving  turnsol  in  a lixivium  of  lime 
and  urine,  or  in  the  volatile  spirit  of  urine ; but  this  has  always  a tendency  to 
purple,  whether  made  by  one  or  the  other  of  these  ways.  A better  blue,  and 
used  in  an  easier  manner,  is  furnished  by  the  Canary  turnsol,  a substance  well 
known  among  the  dyers.  This  need  only  be  dissolved  in  water,  and  drawn  on 
the  place  with  a pencil ; this  penetrates  very  deep  into  the  marble,  and  the  color 
may  be  increased  by  drawing  the  pencil,  wetted  afresh,  several  times  over  the 
same  lines.  This  color  is  subject  to  spread  and  diffuse  itself  irregularly;  but  it 
may  be  kept  in  regular  bounds,  by  circumscribing  its  lines  with  beds  of  wax,  or 
any  other  substance.  It  is  to  be  observed,  that  this  color  should  always  be  laid 
on  cold,  and  no  heat  given  ever  afterwards  to  the  marble ; and  one  great  advan- 
tage of  this  color  is,  that  it  is  easily  added  to  marbles  already  stained  with  any 
other  colors,  and  it  is  a very  beautiful  tinge,  and  lasts  a long  time. 

This  art  has,  in  several  persons’  hands,  been  a very  lucrative  secret,  though 
there  is  scarcely  any  thing  in  it,  that  has  not,  at  one  time  or  another,  been 
published. 

Kircher  has  the  honor  of  being  one  of  the  first  who  published  any  thing 
practicable  about  it.  This  author,  meeting  with  stones  in  some  cabinets,  supposed 
to  be  natural,  but  having  figures  too  nice  and  particular  to  be  supposed  to  be 


12 


PRACTICAL  MASONRY. 


Nature’s  making,  and  these  not  only  on  the  surface,  but  sunk  through  the  whole 
body  of  the  stones,  was  at  the  pains  of  finding  out  the  artist  who  did  the  business ; 
and  on  his  refusing  to  part  with  the  secret  on  any  terms,  this  author,  with  Albert 
Gunter,  a Saxon,  endeavoured  to  find  it  out.  Their  method  is  this.  Take  nitric 
acid  and  nitro-muriatic  acid,  of  each  one  ounce,  sal-ammoniac  one  ounce,  spirit 
of  wine  two  drachms,  about  twenty-six  grains  of  gold,  and  two  drachms  of  pure 
silver ; let  the  silver  be  calcined  and  put  into  a vial,  and  pour  upon  it  the  nitric 
acid ; let  this  stand  some  time,  then  evaporate  it,  and  the  remainder  will  at  first 
appear  of  a blue,  and  afterwards  of  a black  color ; then  put  the  gold  into  another 
vial,  and  pour  the  nitro-muriatic  acid  upon  it,  and  when  it  is  dissolved,  evaporate 
it  as  the  former ; then  put  the  spirit  of  wine  upon  the  sal-ammoniac,  and  let  it  be 
evaporated  in  the  same  manner.  All  the  remainders,  and  many  others  made  in 
the  same  manner  from  other  metals,  dissolved  in  their  proper  acid  menstrua,  are 
to  be  kept  separate,  and  used  with  a pencil  on  the  marble.  These  will  penetrate 
without  the  least  assistance  of  heat,  and,  the  figure  being  traced  with  a pencil  on 
the  marble,  the  several  parts  are  to  be  touched  over  with  the  proper  colors,  and 
this  renewed  daily,  till  the  colors  have  penetrated  to  the  desired  depth  into  the 
stone. 

After  this,  the  mass  may  be  cut  into  thin  plates,  and  every  one  of  them  will 
have  the  figure  exactly  represented  on  both  surfaces,  the  colors  never  spreading. 

The  nicest  method  of  applying  these,  or  the  other  tinging  substances,  to  marble 
that  is  to  be  wrought  into  any  ornamental  works,  and  where  the  back  is  not 
exposed  to  view,  is  to  apply  the  colors  behind,  and  renew  them  often,  till  the 
figure  is  sufficiently  seen  through  the  surface  on  the  front,  though  it  does  not 
quite  extend  to  it.  This  is  the  method  that,  of  all  others,  brings  the  stone  to  a 
nearer  resemblance  of  natural  veins  of  this  kind.  The  same  author  gives  another 
method  to  color  marble,  by  vitriol,  bitumen,  &c.  Forming  a design  of  what  you 
like  upon  paper,  and  laying  the  said  design  between  two  pieces  of  polished 
marble,  then,  closing  all  the  interstices  with  wax,  you  bury  them  for  a month  or 
two  in  a damp  place  ; on  taking  them  up,  you  will  find  that  the  design  you 
painted  on  the  paper  has  penetrated  the  marbles,  and  formed  exactly  the  same 
design  upon  them. 


SECTION  V.  — Granite. 

Granite  is  apparently  the  oldest  and  deepest  of  rocks.  It  is  one  of  the 
hardest  and  most  durable  which  have  been  wrought,  and  is  obtained  in  larger 
pieces  than  any  other  rock.  Granite  is  a compound  stone,  varying  in  color  and 


OF  GRANITE. 


13 


coarseness.  It  consists  of  three  constituent  parts,  united  to  each  other  without  the 
intervention  of  any  cement,  namely,  quartz,  the  material  of  rock-crystal ; feldspar, 
which  gives  it  its  color ; and  lastly  mica,  a transparent,  thin,  or  foliated  substance. 

But  in  order  to  understand  more  perfectly  the  nature  and  qualities  of  granite, 
some  examination  of  its  constituent  parts  is  necessary. 

I.  Quartz  belongs  to  that  class  of  minerals  denominated  earthy  compounds,  or 
stones.  It  embraces  numerous  varieties,  differing  much  in  their  forms,  texture, 
and  other  external  characters.  And  although  but  few  well  defined  external 
characters  apply  to  the  whole  species,  yet  most  of  its  varieties  are  easily  recognized. 

It  is  sufficiently  hard  to  scratch  glass,  and  it  always  gives  sparks  with  steel. 
When  pure,  its  specific  gravity  is  about  2.63,  water  being  1 ; but  in  certain 
varieties  extends  above  and  below  this  term,  depending  on  its  structure,  or  the 
presence  of  foreign  ingredients.  Indeed  the  mean  specific  gravity  of  the  whole 
species  is  about  2.60.  It  is  sometimes  in  amorphous  masses,  and  sometimes  in 
very  beautiful  crystals,  of  which  the  primitive  form  is  a rhomb  slightly  obtuse,  the 
angles  of  its  faces  being  94“  24'  and  85“  36'.  The  secondary  form,  the  most 
common,  is  a six-sided  prism,  terminated  by  six-sided  pyramids.  It  exhibits 
double  refraction,  which  must  be  observed  by  viewing  an  object  through  one  face 
of  the  pyramid  and  the  opposite  side  of  the  prism.  Its  fracture  is  vitreous. 

Chemical  Characters.  All  the  varieties  of  quartz  are  infusible  by  the  blow-pipe, 
and  if  pure,  it  is  scarcely  softened,  even  when  the  flame  is  excited  by  oxygen 
gas.  Before  the  compound  blow-pipe,  a fragment  of  rock-crystal  instantly  melts 
into  a white  glass.  Quartz  is  essentially  composed  of  silex,  or  the  principal 
ingredient  of  flint,  from  93  to  98  parts  being  of  this  substance,  and  the  residue 
alumine,  lime,  water,  or  some  metallic  oxide. 

Among  the  varieties,  are,  — 1.  The  Limpid  Quartz  (Rock-crystal).  This,  the 
most  perfect  variety  of  quartz,  has,  when  crystallized,  received  the  name  of  rock- 
crystal ; indeed  the  same  name  is  sometimes  extended  to  colored  crystals,  when 
transparent.  Limpid  quartz  is  without  color,  and  sometimes  as  transparent  as  the 
most  perfect  glass,  which  it  strongly  resembles.  It  is,  however,  harder  than  glass, 
and  the  flaws  or  bubbles,  which  it  often  contains,  lie  in  the  same  plane,  while 
those  in  glass  are  irregularly  scattered.  The  finest  crystals  are  found  in  veins, 
or  cavities,  in  primitive  rocks,  as  in  granite,  gneiss,  or  mica  slate,  or  in  alluvial  earths. 

In  the  United  States  this  variety  is  not  uncommon.  It  is  found  in  Virginia, 
near  the  North  Mountain.  In  Frederick  county,  Maryland,  crystals  are  scat- 
tered on  the  surface  of  the  ground,  of  perfect  transparency,  with  a splendid  lustre. 
In  New  York,  on  an  island  in  Lake  George,  are  very  fine  crystals,  — and  in 
Vermont,  at  Grafton.  This  variety  is  sometimes  employed  in  jewelry,  for  watch- 
seals,  &LC. 


14 


PRACTICAL  MASONRY. 


2.  Smoky  Quartz.  Objects  seen  through  this  variety,  seem  to  be  viewed 
through  a cloud  of  smoke.  Its  true  color  seems  to  be  clove-brown.  It  is  some- 
times called  smoky  topaz. 

3.  Yellow  Quartz.  Its  color  is  pale  yellow,  sometimes  honey  or  straw-yellow. 
It  has  been  called  citrine ; and  also  false,  or  Bohemian,  topaz. 

4.  Blue  Quartz.  Its  color  is  blue,  or  grayish-blue.  It  is  inferior  in  hardness 
to  the  former  varieties. 

5.  Rose-red  Quartz.  Its  color  is  rose -red,  of  different  shades,  sometimes 
with  a tinge  of  yellow.  It  is  seldom  more  than  semi-transparent.  Its  color, 
which  is  supposed  to  arise  from  manganese,  is  said  to  be  injured  by  exposure  to 
light.  It  has  been  called  Bohemian  ruby.  It  is  sometimes  employed  in  jewelry, 
and  much  esteemed. 

6.  Irised  Quartz.  It  reflects  a series  of  colors,  similar  to  those  of  the  iris  or 
rainbow. 

7.  .dventurine  Quartz.  Its  predominant  color,  which  may  be  red,  yellow, 
gray,  greenish,  blackish,  or  even  white,  is  variegated  by  brilliant  points,  which 
shine  with  silver  or  golden  lustre.  It  is  sometimes  employed  in  ornaments  of 
jewelry. 

8.  Milky  Quartz.  Its  color  is  milk-white,  in  some  cases  a little  bluish  ; and 
it  is  nearly  opaque.  Its  fracture  has  sometimes  a resinous  lustre.  It  is  some- 
times in  small  crystals,  but  more  often  in  large  masses. 

9.  Greasy  Quartz.  Its  colors  are  various,  either  light  or  dark.  Its  fracture 
appears  as  if  rubbed  with  oil. 

10.  Radiated  Quartz.  It  is  in  masses  which  have  a crystalline  structure, 
and  are  composed  of  imperfect  prisms.  These  prisms  usually  diverge  a little, 
or  radiate  from  the  centre,  and  often  separate  with  great  ease. 

11.  Tabular  Quartz.  It  occurs  in  plates  of  various  sizes,  which  are  some- 
times applied  to  each  other  by  the  broader  faces. 

12.  Granular  Quartz.  Its  structure  presents  small  granular  concretions,  or 
grains,  which  are  sometimes  feebly  united.  This  variety  must  be  carefully  dis- 
tinguished from  certain  sandstones  which  it  resembles.  It  may  be  important  in 
the  manufacture  of  glass,  and  certain  kinds  of  stone  ware. 

13.  .Arenaceous  Quartz.  It  is  in  loose  grains,  coarse  or  fine,  either  angular  or 
rounded,  and  constitutes  some  varieties  of  pure  sand.  Certain  sandstones 
appear  to  be  composed  of  this  quartz,  united  by  some  cement. 

14.  Pseiidomorphous  Quartz.  It  appears  under  regular  forms,  such  as  cubes, 
octahedrons,  &c.,  which  do  not  belong  to  the  species.  They  are  opaque,  their 
surfaces  dull,  and  their  edges  often  blunted. 

Common  quartz  never  forms  whole  mountains.  It  is  sometimes  in  large 


OF  GRANITE. 


15 


masses,  or  in  beds,  and  frequently  in  extremely  large  veins,  which  have  been 
mistaken  for  beds.  Quartz,  in  the  form  of  crystallized  grains,  or  of  irregular 
masses  of  various  sizes,  is  abundantly  disseminated  in  granite,  gneiss,  mica  slate, 
&c.,  of  all  which  it  forms  a constituent  part.  It  is  sometimes  in  regular  crystals, 
dispersed  through  the  granite.  In  porphyry,  also,  it  is  sometimes  regularly  crys- 
tallized. It  also  occurs  in  carbonate  of  lime,  anthracite,  &c.  Among  secondary 
rocks,  quartz  is  found,  forming  a greater  part  of  many  sandstones ; also  between 
strata  of  compact  limestone,  of  clay,  or  of  marl,  or  imbedded  in  sulphate  of  lime. 

In  alluvial  earths  it  exists  in  the  form  of  sand.  Quartz  is  often  associated  with 
the  carbonate  and  fluate  of  lime,  sulphate  of  barytes,  and  feldspar,  in  metallic 
veins ; indeed,  it  exists  in  almost  every  metallic  vein. 

Hornblende,  schorl,  epidote,  garnet,  magnetic  iron,  are  also  among  the  minerals 
contained  in  quartz.  Mica  gives  it  a slaty  structure. 

In  some  rare  instances,  bubbles  of  air,  and  even  drops  of  water,  and  bitumen, 
have  been  found  in  quartz.  Although  common  quartz  never  contains  any  organic 
remains,  it  is  sometimes  crystallized  in  fossil  wood. 

Quartz  is  found  very  abundantly  in  most  of  the  Northern  and  Middle  States. 

We  have  already  seen  that  certain  varieties  of  quartz  are  employed  in  jewelry. 
It  is  also  used,  especially  the  sandy  variety,  in  the  manufacture  of  glass  ; also  in 
the  preparation  of  smalt  and  certain  enamels. 


II.  Feldspar.  This  important  and  widely  distributed  mineral  has,  in  most  of 
its  varieties,  a structure  very  distinctly  foliated.  It  scratches  glass,  and  gives 
sparks  with  steel,  but  its  hardness  is  a little  inferior  to  that  of  quartz.  When  in 
crystals  or  crystalline  masses,  it  is  very  susceptible  of  mechanical  division,  at 
natural  joints,  which,  in  two  directions  perpendicular  to  each  other,  are  extremely 
perfect ; but  in  the  third  direction  they  are  usually  indistinct. 

The  primitive  form,  thus  obtained,  is  an  oblique-angled  parallelogram,  whose 
sides  are  inclined  to  each  other  in  angles  of  90°,  120°,  and  111°  28'.  The  four 
sides,  produced  by  the  two  divisions  perpendicular  to  each  other,  have  a brilliant 
polish,  while  the  two  other  sides  are  dull ; this  is  a distinctive  character  of  great 
importance.  Its  specific  gravity  usually  lies  between  2.43  and  2.70.  It  possesses 
double  refraction,  which,  however,  is  not  easily  observed.  It  is  usually  phospho- 
rescent, by  friction,  in  the  dark. 

Chemical  Characters.  Before  the  blow-pipe  it  melts  into  a white  enamel,  or 
glass,  more  or  less  translucent.  The  results  of  analysis  have  not  yet  been  per- 
fectly satisfactory  in  regard  to  the  true  composition  of  feldspar.  It  appears  prob- 
able, however,  that  not  only  silex  and  alumine,  but  also  lime  and  potash,  are 
essential  ingredients.  In  a specimen  of  green  feldspar,  Vauquebin  found  62.88 


16 


PRACTICAL  MASONRY. 


parts  of  silex,  17.02  of  alumine,  13.0  of  potash,  3.0  of  lime,  and  1.0  of  oxide  of 
iron,  = 96.85  in  a hundred  parts. 

Several  of  the  varieties  of  feldspar  deserve  notice. 

1.  Common  Feldspar.  This  variety  occurs  in  fragments  often  rolled,  also  in 
grains  in  sand,  but  more  commonly  in  masses  of  moderate  size,  forming  an  ingre- 
dient of  compound  minerals.  It  is  not  unfrequently  in  regular  crystals  of  the 
primitive  form,  already  mentioned. 

The  crystals  of  feldspar,  seldom  very  small,  are  sometimes  several  inches  both 
in  diameter  and  length ; their  faces  are  shining,  and  their  edges  sometimes  very 
perfect.  Their  prevailing  form  is  an  oblique  prism,  whose  sides  are  unequal,  and 
vary  in  number,  from  four  to  ten.  The  terminating  faces,  of  which  two  are 
commonly  longer  than  the  others,  are  subject  to  great  variation  in  number  and 
extent ; indeed,  they  often  seem  to  have  no  symmetry  in  their  arrangement,  a 
circumstance  which  arises  from  the  obliquity  and  irregularity  of  the  primitive 
form. 

The  longitudinal  fracture  is  foliated,  and  its  lustre  more  or  less  shining  and 
vitreous,  sometimes  pearly,  especially  in  certain  spots ; the  cross  fracture  is 
uneven  or  splintery,  and  nearly  dull.  It  is  easily  broken,  and  falls  into  rhomboidal 
fragments,  which  have  four  polished  faces.  The  folia  are  sometimes  curved,  or 
arranged  like  the  petals  of  a flower. 

It  is  more  or  less  translucent,  sometimes  nearly  or  quite  opaque,  and  presents 
a great  variety  of  coloi’s.  Among  these  are  white,  tinged  with  gray,  yellow,  green, 
or  red  ; gray,  often  with  a shade  of  blue ; several  shades  of  red,  as  flesh  or 
blood-red ; to  which  must  be  added  green,  yellow,  brown,  or  even  black. 

This  variety  is  abundant,  and  constitutes  an  essential  ingredient  of  granite, 
gneiss,  sienite,  and  greenstone.  Of  granite  and  sienite  it  sometimes  forms 
two  thirds  of  the  whole  mass.  It  exists  also  in  argillite  and  porphyry,  &c.  Its 
crystals,  though  sometimes  imbedded,  are  more  often  found  in  the  fissures  or 
cavities  of  these  rocks,  and  are  sometimes  associated  with  epidote,  axinite, 
chronite,  amianthus,  carbonate  of  lime,  quartz,  magnetic  oxide  of  iron,  &c. 

2.  Green  Feldspar.  The  variety  is  rare,  and  has  an  apple-green  color,  varying 
somewhat  in  intensity,  and  sometimes  marked  with  whitish  stripes. 

3.  Adularia.  This  is  the  most  perfect  variety  of  feldspar,  and  bears  to  com- 
mon feldspar,  in  many  respects,  the  relation  of  rock-crystal  to  common  quartz. 
It  is  more  or  less  translucent,  and  sometimes  transparent  and  limpid.  Its  color  is 
white,  either  a little  milky,  or  with  a tinge  of  green,  yellow,  or  red.  But  it  is 
chiefly  distinguished  by  presenting,  when  in  certain  positions,  whitish  reflections, 
which  are  often  slightly  tinged  with  blue  or  green,  and  exhibit  a pearly  or  silver 
lustre.  Adularia  is  sometimes  cut  into  plates  and  polished.  The  fish’s  eye  moon- 


OF  GRANITE. 


17 


stone  and  argentine  of  lapidaries  come  chiefly  from  Persia,  Arabia,  and  Ceylon, 
and  belong  to  adularia,  as  do  also  the  water-opal  and  girasole  of  the  Italians. 

4.  Opalescent  Feldspar.  This  very  beautiful  variety  is  distinguished  by  its 
property  of  reflecting  light  of  different  colors,  which  appear  to  proceed  from  its 
interior.  Its  proper  color  is  gray,  often  dark  or  blackish-gray,  and  sometimes 
specimens  are  marked  with  whitish  spots  or  veins.  But  when  held  in  certain 
positions  it  reflects  a very  lively  and  beautiful  play  of  colors,  embracing  almost 
every  shade  of  green  and  blue,  and  several  shades  of  yellow,  red,  gray,  and 
brown.  These  colors  are  usually  confined  to  certain  spots,  and  even  the  same 
spot  changes  its  color  in  different  positions.  It  is  much  esteemed  in  jewelry. 

5.  Acenturine  Feldspar.  Its  colors  are  various  ; but  it  contains  little  spangles 
or  points,  which  reflect  a brilliant  light. 

6.  Petuntze.  It  is  nearly  or  quite  opaque,  and  its  color  is  usually  whitish  or 
gray.  It  has,  in  most  cases,  less  lustre  than  common  feldspar.  It  most  usually 
occurs  in  beds.  Its  powder  is  said  to  have  a slightly  saline  taste.  It  is  used  in 
the  manufacture  of  porcelain,  both  for  an  enamel  and  its  composition. 

7.  Granular  Feldspar.  It  is  nearly  or  quite  opaque,  and  imperfectly  foliated. 
It  varies  much  in  hardness,  and  is  sometimes  friable  between  the  fingers.  Its 
color  is  usually  white,  and  sometimes  strongly  resembles  masses  of  white  sugar. 
Feldspar  is  found  in  the  Northern,  and  most  of  the  Middle  States. 

III.  Mica.  Mica  appears  to  be  always  the  result  of  crystallization,  but  it  is 
rarely  found  in  regular,  well-defined  crystals.  Most  commonly  it  appears  in 
thin,  flexible,  elastic  laminae,  which  exhibit  a high  polish  and  strong  lustre.  These 
laminae  have  sometimes  an  extent  of  many  square  inches  ; and  from  this  grad- 
ually diminish,  till  they  become  mere  spangles.  They  are  usually  found  united 
into  small  masses,  extremely  variable  in  thickness,  or  into  crystals  more  or  less 
regular ; their  union,  however,  is  so  very  feeble,  that  they  are  easily  separable, 
and  may  be  reduced  to  a surprising  degree  of  tenuity.  In  this  state  their  surface 
becomes  irised,  and  their  thickness  does  not  exceed  a millionth  part  of  an  inch. 

The  crystals  of  mica  are  sometimes  right  prisms  with  rhombic  bases,  whose 
angles  are  120°  and  62°.  This  is  also  the  primitive  form,  in  which  one  side  of 
the  base  is  to  the  height  of  the  prism  nearly  as  3 to  8. 

The  structure  of  mica  is  always  foliated,  but  the  foliae  may  be  straight,  curved, 
or  undulated.  The  surface  has  a shining  or  splendent  lustre,  which  is  usually 
metallic,  sometimes  like  that  of  silver  or  gold  ; and  sometimes  like  that  of  polished 
glass.  It  is  easily  scratched  by  a knife,  and,  in  most  cases,  even  by  the  finger- 
nail. Its  surface  is  smooth  to  the  touch,  and  very  seldom  slightly  unctuous ; its 
powder  is  dull,  grayish,  and  feels  soft.  It  is  often  transparent ; in  other  cases  it 

3 


18 


PRACTICAL  MASONRY, 


is  only  translucent,  sometimes  at  the  edges  only.  Its  colors  are  silver-white,  gray, 
often  tinged  with  yellow,  green,  or  black ; also,  brown,  reddish,  and  green. 

Its  specific  gravity  extends  from  2.53  to  2.93 ; and  when  rubbed  on  sealing- 
wax,  it  communicates  to  the  wax  negative  electricity. 

Chemical  Characters.  It  is  fusible  by  the  blow-pipe,  though  sometimes 
with  difficulty,  into  enamel,  which  is  usually  gray  or  black.  The  colored  varieties 
are  the  most  easily  fusible ; and  black  mica  gives  a black  enamel,  which  often 
moves  the  needle.  It  contains,  according  to  Klaproth,  silex  48.0,  alumine  34.25, 
potash  8.75,  oxyd  of  iron  4.5,  oxyd  of  manganese  0.5,^=  96.  Sometimes  the 
potash  is  in  greater  proportion,  and  in  black  mica  the  oxyd  of  iron  is  sometimes 
as  high  as  22  per  cent.  Mica  is  subject  to  decomposition  by  exposure  to  the 
atmosphere. 

The  following  are  the  most  important  varieties  of  mica : — 

1.  Laminated  Mica.  It  occurs  in  large  plates,  which  often  contain  many 
square  inches.  It  has  been  called  Muscovy  glass,  or  talc,  being  found  abundantly 
in  that  country. 

2.  Lamellar  Mica.  This  is  the  more  common  variety.  It  exists  in  small 
foliae,  either  collected  into  masses,  or  disseminated  in  other  minerals.  It  is 
sometimes  in  extremely  minute  scales,  which,  when  detached  from  the  mass, 
appear  like  sand. 

3.  Prismatic  Mica.  This  variety  is  not  common.  The  laminae  are  easily 
divisible,  parallel  to  their  edges,  into  minute  prisms,  or  even  into  delicate  filaments. 
The  edges  of  the  laminae  have  usually  more  lustre  than  those  of  the  other 
varieties. 

Although  mica  never  occurs  in  beds,  or  large  insulated  masses,  there  is  no 
substance  more  universally  diffused  through  the  mineral  kingdom.  It  is  an 
essential  ingredient  in  granite,  gneiss,  and  mica-slate ; and  occurs  also  in  sienite, 
porphyry,  and  other  primitive  rocks.  Mica  occurs  also  in  greenstone,  basalt, 
sandstone,  and  other  secondary  rocks,  especially  in  sandstone  and  shell,  which 
accompany  coal. 

In  the  United  States  mica  is  very  abundant. 

It  has  been  employed,  instead  of  glass,  in  the  windows  of  dwelling-houses ; 
also  in  ships  of  war,  because  it  is  not  liable  to  be  broken  by  the  concussion 
produced  by  the  discharge  of  cannon.  In  lanterns  it  is  superior  to  horn,  being 
more  transparent,  and  not  so  easily  injured  by  heat.  When  in  thin,  transparent 
laminae,  sufficiently  large,  it  is  useful  to  defend  the  eyes  of  those  who  travel, 
against  high  winds  and  severe  storms  of  snow.  When  of  suitable  color  and  in 
minute  scales,  it  is  employed  to  ornament  paper,  which  is  then  said  to  be  frosted ; 
the  scales  of  mica  are  made  to  adhere  by  a solution  of  gum  or  glue. 

These  are  the  ingredients  of  which  granite  is  composed. 


OF  GRANITE. 


19 


The  structure  of  granite  is  granular;  but  the  grains  are  extremely  variable, 
both  in  size  and  form.  Most  frequently  the  size  of  the  grains  lies  between  that 
of  a pin’s  head  and  a nut.  Sometimes,  however,  they  are  several  inches,  and 
even  more  than  a foot,  in  their  dimensions,  and  sometimes  they  are  so  minute, 
that  the  mass  resembles  a sandstone,  or  even  appears  almost  homogeneous  to 
the  naked  eye. 

The  forms  of  these  grains  are,  in  general,  altogether  irregular,  like  those  of  the 
fragments  of  most  minerals.  In  some  granites  the  feldspar  or  quartz,  or  even 
the  mica,  is  in  crystals  more  or  less  regular. 

The  ingredients  of  granite  vary  much  in  their  proportions ; but,  in  general,  the 
feldspar  is  most  abundant,  and  the  mica  is  usually  in  the  smallest  proportion. 
Their  arrangement  is  also  various : sometimes,  while  the  feldspar  and  quartz  are 
mingled  with  considerable  uniformity,  the  mica  appears  only  in  scattered  masses, 
or  is  found  investing  grains  of  feldspar  and  quartz  on  all  sides ; in  other  cases 
the  feldspar  and  mica,  or  quartz  and  mica,  are  mingled,  while  the  third  ingredient 
appears  in  small,  distinct  masses. 

One  of  the  ingredients  of  this  rock,  most  frequently  the  quartz  or  mica,  may 
be  entirely  wanting,  through  a greater  or  less  portion  of  the  mass,  so  that  speci- 
mens of  true  granite  (as  it  is  sometimes  called)  contain  only  two  ingredients. 

The  predominant  color  of  granite  usually  depends  on  that  of  the  feldspar, 
which  may  be  white  or  gray,  sometimes  with  a shade  of  red,  yellow,  blue,  or 
green,  and  sometimes  it  is  flesh-red.  The  quartz  may  be  white,  grayish-white, 
or  gray,  sometimes  very  dark ; but  it  is  usually  vitreous  and  translucent.  The 
mica  may  be  black,  brown,  gray,  silver-white,  yellowish,  or  violet. 

The  simple  minerals  which  enter  into  the  composition  of  granite  are,  in  general, 
so  intimately  united,  that  the  mass  is  firm  and  solid ; but  some  varieties  are  brittle, 
and  easily  become  disintegrated.  The  feldspar  sometimes  undergoes  a partial 
decomposition,  losing  its  lustre,  hardness,  and  foliated  structure,  while,  at  other 
times,  it  is  converted  into  porcelain  clay.  The  mica,  also,  when  exposed  to  the 
open  air,  is  subject  to  alteration,  or  even  decomposition.  Sulphuric  acid  is  often 
generated  by  the  decomposition  of  the  sulphuret  of  iron,  disseminated  in  che 
granite,  and  this  acid  acts  upon  the  mica  in  its  vicinity,  thus  producing  a soft 
substance,  and  diminishing  the  firmness  of  the  granite.  Granite  which  embraces 
short  is  also  liable  to  disintegration. 

The  specific  gravity  of  granite  generally  lies  between  2.5  and  2.6,  but  is 
sometimes  higher. 

Among  the  varieties  of  granite  are,  — 

1.  Graphic  Granite.  This  very  beautiful  variety  of  granite  is  composed 
chiefly  of  feldspar  and  quartz.  The  feldspar  is  very  abundant,  forming  a base, 


20 


PRACTICAL  MASONRY. 


in  which  quartz,  under  various  forms,  lies  imbedded.  When  this  granite  is 
broken  in  a direction  perpendicular  to  that  in  which  the  quartz  traverses  the 
feldspar,  the  surface  of  the  fracture  ordinarily  presents  the  general  aspect  of 
letters^  arranged  in  parallel  lines  ; and  hence  its  name.  These  letters  of  gray, 
vitreous  quartz,  on  a shining  and  polished  tablet  of  white  or  flesh-colored  feld- 
spar, appear  extremely  beautiful.  It  is  principally  this  variety  of  granite  which, 
by  its  decomposition,  furnishes  porcelain  clay. 

2.  Globular  Granite.  This  is  composed  of  large,  globular,  distinct  concretions, 
which  are  sometimes  several  feet  in  diameter.  These  concretions  are  united  by 
a kind  of  granite,  which  is  readily  disintegrated,  thus  leaving  the  globular  masses 
detached  from  each  other. 

3.  Porphyritic  Granite.  This  variety  is  produced,  when  large  crystals  of 
feldspar  are  interspersed  in  a fine-grained  granite. 

Granite  is  always  a primitive  rock ; and  never  embraces  any  organic  remains 
of  animals  or  vegetables. 

It  exists  very  extensively,  and  in  many  countries  it  occurs  in  immense  quan- 
tities. It  constitutes  a large  portion  of  many  of  the  highest  mountains,  of  which 
it  appears  to  form  the  central  parts,  as  well  as  the  summits.  It  is  more  or  less 
abundant  in  the  mountains  of  Scotland  and  Germany ; the  Alps,  the  Carpathian, 
the  Uralian,  and  the  Altaian  mountains ; the  Andes,  and  the  United  States. 

Granite  is  chiefly  used  as  a building  stone.  It  is  split  from  the  quarries  by 
rows  of  iron  wedges,  driven  simultaneously  in  the  direction  of  the  intended  fis- 
sure. This  method  is  thought  by  Brard  to  have  been  known  to  the  ancient 
Romans  and  Egyptians.  The  blocks  are  afterwards  hewn  to  a plane  surface, 
by  the  strokes  of  a sharp-edged  hammer.  Granite  is  also  chiselled  into  capitals 
and  decorative  objects,  but  this  operation  is  difficult,  owing  to  its  hardness  and 
brittleness.  It  is  polished,  by  long-continued  friction,  with  sand  and  emery. 

The  largest  mass  of  granite  knowm  to  have  been  transported,  in  modem 
times,  is  the  pedestal  of  the  equestrian  statue  of  Peter  the  Great,  at  St.  Peters- 
burg. It  is  computed  to  weigh  three  million  pounds,  and  w^as  transported  nine 
leagues,  by  rolling  it  on  cannon-balls;  those  of  iron  being  crushed,  others  of 
bronze  were  substituted.  Sixty  granite  columns,  at  St.  Petersburg,  consist  each 
of  a single  stone,  twenty  feet  high.  The  columns  in  the  portico  of  the  Pan- 
theon, at  Rome,  which  are  thirty-six  feet  eight  inches  high,  are  also  of  granite. 
The  shaft  of  Pompey’s  Pillar,  in  Egypt,  is  sixty-three  feet  in  height,  and  of  a 
single  piece.  It  is  said  to  be  of  red  granite,  but  is  possibly  sienite.  In  the  east- 
ern part  of  the  United  States,  a beautiful  white  granite  is  found  in  various  places, 
and  is  now  introduced  into  building.  The  Quincy  Market-house  in  Boston,  the 
United  States  Bank,  the  Tremont  House,  the  Tremont  Temple,  &c.,  are  made 
of  it. 


OF  SIENITE. 


21 


SECTION  VI.  — SiENiTE. 

This  rock  is  related  to  granite,  and  resembles  it  in  its  general  characters. 
Feldspar  and  hornblend  may  be  considered  its  constant  and  essential  ingredients. 
Feldspar  is  the  most  abundant  ingredient,  and  has  already  been  described  (see 
Granite)  ; but  as  it  is,  however,  the  presence  of  hornblend  as  a constituent 
part  which  distinguishes  this  rock  from  granite,  some  account  of  it  may  be 
useful. 

I.  Hornblend  is  a very  common  mineral,  and  may,  in  general,  be  easily 
recognized.  Sometimes  it  is  in  regular  and  distinct  crystals,  but  more  common- 
ly it  appears  in  masses,  composed  of  laminae,  or  fibres,  variously  aggregated, 
the  result  of  confused  crystallization. 

When  its  structure  is  sufficiently  regular,  mechanical  division  is  easily  effected 
in  a longitudinal  direction ; and  its  crystals  are  found  to  be  composed  of  laminae, 
situated  parallel  to  the  sides  of  an  oblique  four-sided  prism,  with  rhombic  bases ; 
the  sides  of  this  prism  are  inclined  to  each  other,  at  angles  of  124°  34'  and 
55°  26'.  The  longitudinal  fracture  is  of  course  foliated,  and  usually  presents 
the  broken  edges  of  many  laminae  extending  one  beyond  another. 

Hornblend  usually  scratches  glass,  and  sometimes  with  difficulty  gives  sparks 
with  steel.  Its  powder  is  dry,  and  not  soft  to  the  touch.  It  is  often  opaque, 
sometimes  translucent.  It  is  generally  black  and  green,  often  intermixed.  Its 
specific  gravity  is  about  3.20. 

Chemical  Characters.  Before  the  blow-pipe  it  melts  with  considerable  ease, 
and  forms  black  or  grayish-black  glass,  or  grayish  enamel.  It  yields,  by  analy- 
sis, silex,  alumine,  magnesia,  and  lime,  but  in  variable  proportions.  Its  colors 
are  produced  by  the  oxyds  of  iron  and  of  chrome. 

Masses  of  hornblend,  whether  fibrous,  lamellar,  or  nearly  compact,  possess  a 
remarkable  tenacity,  which  renders  them  tough  and  difficult  to  break ; indeed, 
a considerable  cavity  may  often  be  produced  by  the  hammer,  before  the  mass 
breaks.  They  exhale,  when  moistened  by  the  breath,  a peculiar  argillaceous 
odor. 

Some  of  the  varieties  are,  — 

1.  Basaltic  Hornblend,  which  is  found  in  lava  and  volcanic  scoriae,  and  very 
often  in  basalt ; and  hence  its  name.  It  is  almost  always  in  distinct  crystals, 
whose  color  is  a pure  black,  sometimes  slightly  tinged  with  green,  or  brownish, 
by  decomposition.  Their  surface  is  sometimes  strongly  shining,  at  other  times 


22 


PRACTICAL  MASONRY. 


dull,  and  invested  with  a ferruginous  crust.  Its  structure  is  more  foliated  than 
that  of  other  varieties,  and  its  crystals  more  brittle. 

2.  Lamellar  Hornblend.  Its  masses  are  sometimes  composed  merely  of  lam- 
ellar, and  sometimes  of  granular,  concretions  of  various  sizes,  having  a lamellated 
structure.  Hence  the  fracture  is  foliated,  but  the  foliae  are  variously  inclined 
and  interlaced. 

3.  Fibrous  Hornblend.  It  occurs  in  masses,  composed  of  acicular  crystals  or 
fibres,  either  broad  or  narrow,  parallel  or  interlaced. 

4.  Slaty  Hornblend,  or  Hornblend  Slate.  This  variety  scarcely  differs  from 
the  preceding,  except  in  the  slaty  structure  of  its  masses.  For  each  individual 
layer  is  composed  of  very  minute  fibres,  diverging  in  bundles,  or  promiscuously, 
and  often  interlaced. 

Hornblend  is  an  essential  ingredient  in  sienite  and  greenstone,  as  well  as  in 
basalt  and  lava. 

Sienite,  being  composed  of  these  two  ingredients,  is  usually  granular ; but  the 
grains  are  sometimes  coarse,  and  sometimes  very  fine.  In  some  instances  its 
structure  is  slaty.  When  this  rock  is  very  fine  grained,  and,  at  the  same  time, 
contains  large  crystals  of  feldspar,  it  constitutes  sienitic  porphyry. 

The  feldspar,  whose  foliated  texture  is  often  very  distinct,  is  most  frequently 
reddish  or  whitish ; but  sometimes  it  receives  a greenish  tinge  from  the  horn- 
blend, or  from  epidote. 

Sienite  is  sometimes  found  resting  on  granite,  gneiss,  mica-slate,  or  argillite, 
and  sometimes  it  is  associated  with  greenstone  and  argillaceous  porphyries. 

This  rock  is  often  altered  at  the  surface  by  the  action  of  the  weather,  more 
especially  in  those  varieties  which  contain  an  uncommon  proportion  of  feldspar. 
It  often  is  susceptible  of  a good  polish  ; and  may  be  employed  for  the  same 
purposes  as  porphyry.  Its  name  is  derived  from  that  of  Sienna,  a city  in  Egypt, 
where  it  is  found  in  abundance,  and  constitutes  the  material  of  many  of  the  obe- 
lisks. The  Romans  imported  it  for  purposes  of  statuary  and  architecture. 

Sienite  is  obtained  in  large  pieces,  and  possesses  all  the  valuable  qualities  of 
granite  as  a building  stone.  It  is  somewhat  harder  than  granite,  and  more  dif- 
ficult to  chisel.  It  is  found  abundantly  near  Boston,  at  Weymouth,  Brighton, 
Quincy,  &c.,  and  is  introduced  into  many  structures.  The  Washington  Bank 
and  the  Bunker  Hill  Monument  consist  of  this  stone.  It  is  rendered,  by  its  ex- 
treme hardness,  one  of  the  best  materials  for  macadamizing  roads.  The  railway 
at  Quincy  is  built  for  transporting  this  stone  from  the  quarry  to  the  sea,  and  it  is 
there  commonly  called  the  Quincy  stone. 


OF  GREENSTONE. 


23 


SECTION  VII. — Greenstone. 

SiENiTE  and  greenstone  are  essentially  composed  of  the  same  ingredients, 
x\2i.mQ\y,  feldspar  and  hornblend.  And  the  two  rocks  do,  in  fact,  pass  into  each 
other  by  insensible  shades.  But  in  greenstone  the  hornblend  predominates, 
while  in  sienite  the  feldspar  is  the  most  abundant  ingredient.  This  frequently 
gives  to  this  stone  more  or  less  of  a greenish  tinge,  especially  when  it  is  mois- 
tened ; hence  the  name  of  this  rock.  Sometimes  the  tinge  of  green  is  consid- 
erable lively ; sometimes,  also,  its  color  is  a dark  gray,  or  grayish-black.  In 
short,  its  color,  especially  at  the  surface,  is  often  modified  by  the  presence  of 
oxyd  of  iron. 

It  presents  a considerable  diversity  of  aspect,  depending  on  the  general  struc- 
ture, or  on  the  size,  proportion,  disposition,  and  more  or  less  intimate  mixture 
of  its  constituent  parts.  From  greenstone,  with  a coarse  granular  structure,  to 
those  varieties  whose  texture  is  so  finely  granular  that  the  tw'o  ingredients  can 
scarcely  be  perceived,  there  is  a gradual  passage,  exhibiting  every  intermediate 
step.  Indeed,  the  grains  are  sometimes  so  minute,  and  so  uniformly  and  in- 
timately mingled,  that  the  mass  appears  altogether  homogeneous,  and  the  dif- 
ferent ingredients  are  hardly  perceptible,  even  with  a glass. 

It  sometimes  presents  prisms  or  columns  of  various  size.  These  prisms 
may  have  from  three  to  seven  sides,  and  are  often  quite  regular.  Many  green- 
stones are  susceptible  of  a polish.  It  occurs  in  beds,  more  or  less  large,  and 
sometimes  forms  whole  mountains. 

Greenstone  is  common  in  the  United  States.  When  this  rock  breaks  into 
prismatic  fragments,  it  forms  a very  useful  building  stone.  Most  of  its  varie- 
ties, when  heated  red-hot,  plunged  into  cold  water,  and  pulverized,  become  a 
good  substitute  for  puzzolana  in  preparing  water-proof  mortar  for  the  con- 
struction of  walls,  cellars,  docks,  piers,  &c.  This  rock  has  sometimes  received 
the  appellation  of  trap,  which  seems  to  be  a generic  term,  applied  to  those 
stones  which  consist  principally  of  hornblend. 


SECTION  VIII. — Sandstone,  or  Freestone. 

Sandstone  is  composed,  generally,  of  grains  of  quartz  (see  Granite),  united 
by  a cement,  which  is  never  very  abundant,  and  often,  indeed,  nearly  or  quite 
invisible.  These  grains  are  sometimes  scarcely  distinguishable  by  the  naked 
eye,  and  sometimes  their  magnitude  is  equal  to  that  of  a nut  or  an  egg. 


24 


PRACTICAL  MASONRY. 


The  cement  is  variable  in  quantity,  and  may  be  calcareous  or  merely  argil- 
laceous or  siliceous.  When  siliceous,  the  mineral  much  resembles  quartz.  The 
texture  of  some  sandstones  is  very  close,  while  that  of  others  is  so  loose  and 
porous  as  to  permit  the  passage  of  water. 

Some  varieties  are  sufficiently  hard  to  give  fire  with  steel,  while  others  are 
friable,  and  may  be  reduced  to  powder  even  by  the  fingers ; this  is  often  the 
case  with  those  sandstones  whose  cement  is  marly. 

Its  fracture  is  always  granular  or  earthy  ; in  some  instances  it  may,  at  the 
same  time,  be  splintery.  Some  sandstones  have  a slaty  structure,  arising  from 
scattered  plates  of  mica,  and  have  been  called  sandstone  slate. 

Its  most  common  color  is  gray  or  grayish ; it  is  sometimes  reddish,  or  reddish- 
brown.  In  some  cases  the  color  is  uniform,  in  others  variegated. 

Among  the  varieties  are,  — 

1.  Red  Sandstone.  The  grains  of  this  variety  are  usually  coarse,  and  united 
by  an  argillaceous  cement,  which  is  at  the  same  time  ferruginous ; hence  the 
dark  reddish  or  reddish-brown  color  which  it  presents. 

2.  Variegated  Sandstone.  This  presents  a variety  of  colors ; as  yellow,  green, 
brown,  red,  and  white,  which  are  usually  arranged  in  stripes,  or  zones,  either 
straight  or  wavering.  It  has  commonly  a close  texture  and  hne  grain ; but  it 
very  often  embraces  roundish  masses  of  clay,  which  often  fall  out  when  ex- 
posed to  the  weather,  and  diminish  its  value  for  the  purposes  of  architecture. 

3.  White  Sandstone.  This  includes  many  of  the  more  common  and  valua- 
ble varieties  of  sandstone.  Its  color  is  whitish-gray  or  gray,  and  generally  uni- 
form ; but  sometimes  it  is  marked  with  reddish  spots.  Its  cement  is  often  cal- 
careous. It  is  well  adapted  for  various  uses  in  the  arts. 

Sandstone  is,  in  general,  more  or  less  distinctly  stratified.  Its  beds  are  very 
often  nearly  or  quite  horizontal ; but  sometimes,  especially  in  the  older  varie- 
ties, they  are  much  inclined,  or  even  vertical.  Sometimes,  also,  when  in  the 
vicinity  of  primitive  mountains,  its  beds  are  thin,  and  much  bent  or  waved. 
Beds  of  sandstone  are  sometimes  intersected  with  fissures  perpendicular  to  the 
direction  of  the  strata,  and  hence  fall  into  tabular  masses,  which  are  often  very 
large. 

Sandstone  is  found  in  various  parts  of  the  United  States,  and  is,  in  some 
of  its  varieties,  very  useful  , in  the  arts.  It  is  frequently  known  by  the  name 
of  freestone.  When  sufficiently  solid,  it  is  employed  as  a building  stone.  In 
most  cases,  it  is  of  moderate  hardness,  and  cuts  equally  well  in  all  directions. 
Some  varieties  naturally  divide  into  prismatic  masses.  It  is  sometimes  used 
as  millstones,  for  grinding  meal,  or  for  wearing  down  other  minerals,  prepar- 
atory to  a polish.  These  stones,  when  rapidly  revolving,  have  been  known 


OF  GNEISS. 


25 


to  burst  with  a loud  and  dangerous  explosion.  When  the  texture  is  sufficiently 
loose  and  porous,  it  is  employed  for  filtering  water.  Some  varieties  are  used  for 
whetstones. 

Sandstone  is  used  for  buildings,  in  various  parts  of  Europe.  In  Africa,  the 
Temple  of  Hermopolis  is  composed  of  enormous  masses  of  this  stone.  In  Amer- 
ica, the  Capitol  at  Washington  is  of  the  Potomac  freestone  or  sandstone;  likewise 
the  facade  of  St.  Paul’s  Church,  in  Boston. 


SECTION  IX.  — Gneiss. 

This  rock,  like  granite,  is  composed  of  feldspar,  quartz,  and  mica.  But  there 
is  in  gneiss  less  feldspar  and  more  mica,  than  in  granite  ; but  even  in  this  sub- 
stance the  feldspar  appears  in  many  cases  to  be  the  predominant  ingredient.  Its 
structure  is  always  more  or  less  distinctly  slaty,  when  viewed  in  the  mass  ; although 
individual  layers,  composed  chiefly  of  feldspar  and  quartz,  may  possess  a granular 
structure.  The  layers,  whether  straight  or  curved,  are  frequently  thick ; but 
often  vary  considerably  in  the  same  specimen;  and  when  the  mineral  is  broken 
perpendicular  to  the  direction  of  the  strata,  its  fracture  has  commonly  a striped 
aspect.  It  splits  easily  in  the  direction  of  the  strata,  especially  when  a separation 
is  made  in  a layer  of  mica.  When  gneiss  is  broken  in  the  direction  of  the  strata, 
the  mica  often  seems  more  abundant  than  the  other  ingredients,  but  when  seen  on 
the  cross  fracture,  it  obviously  exists  in  less  proportion  than  the  feldspar  or  quartz. 

The  plates,  or  foliae,  of  mica,  are  usually  arranged  parallel  to  the  direction  of  the 
strata,  and  in  some  varieties  are  chiefly  collected  into  thin  parallel  layers,  separated 
by  those  of  feldspar  and  quartz.  The  grains  of  feldspar  are  often  flattened  in  the 
direction  of  the  strata. 

The  feldspar  is  usually  white,  or  gray,  sometimes  with  a tinge  of  yellow  or  red. 
The  quartz  is  ordinarily  grayish-white  ; and  the  mica  is  often  black,  but  some- 
times gray. 

The  hardness  of  gneiss  is  variable  ; and  the  feldspar  and  mica  are  subject  to 
the  same  changes  as  when  they  exist  in  granite. 

Gneiss,  like  granite,  never  embraces  any  petrifactions,  and  is  always  a primitive 
rock. 

When  gneiss  occurs  with  granite,  it  usually  lies  immediately  over  the  granite  ; 
or,  if  the  strata  be  highly  inclined,  it  appears  rather  to  rest  against  the  granite, 
than  to  be  incumbent  upon  it. 

This  rock,  as  has  been  intimated,  assumes  sometimes  a granular  structure,  and 
passes,  by  imperceptible  shades,  into  granite. 

4 


26 


PRACTICAL  MASONRY. 


Mountains  composed  of  gneiss  are  seldom  so  steep  as  those  of  granite. 

This  rock  is  abundant  in  the  United  States.  It  is  useful  for  many  purposes, 
in  consequence  of  the  facility  with  which  it  splits  into  masses  of  regular  form. 


SECTION  X.— Mica-slate. 

Mica-slate  is  essentially  composed  of  mica  and  quartz  (see  Granite),  which 
are,  in  general,  more  or  less  intimately  mingled ; but  sometimes  the  two  ingredi- 
ents alternate  in  distinct  layers.  Although  the  proportions  of  mica-slate  are  varia- 
ble, the  mica  usually  predominates. 

The  quartz  is  most  frequently  grayish-white  ; but  the  mica  may  be  whitish,  or 
gray,  bluish-gray,  or  greenish,  brownish,  deep  blue,  or  nearly  black. 

Its  structure  is  always  distinctly  slaty,  more  so  than  that  of  gneiss ; and  its 
masses  are  often  very  fissile.  The  layers  are  sometimes  straight  and  sometimes 
undulated.  In  some  varieties  the  texture  is  very  fine,  and  the  foliae  of  mica  so 
small  that  they  are  scarcely  discernible  by  the  eye,  unless  their  aggregation  be 
previously  destroyed  by  heat. 

This  rock  has  often  a very  high  lustre,  when  viewed  by  the  reflected  rays  of 
the  sun.  It  is,  however,  subject  to  decomposition,  by  which  its  aspect  is  much 
altered. 

Mica-slate  is  a primitive  rock  ; but  seldom  appears  in  high,  steep  cliffs  like 
those  of  granite.  When  it  forms  hills,  the  summits  are  usually  much  rounded. 
It  abounds  in  ores,  which  exist  both  in  beds  and  veins  ; but  more  frequently  in 
beds.  It  is  less  abundant  in  the  United  States  than  gneiss.  It  is  sometimes 
split  into  tabular  masses,  and  employed  for  many  common  purposes.  It  is 
extremely  useful  in  constructing  the  hearths  and  sides  of  furnaces  for  smelting 
iron. 


SECTION  XL — Slate. 

Slate  is  an  argillaceous  stone,  characterized  by  easily  splitting  into  large,  thin, 
and  straight  layers,  or  plates,  which  are  sonorous  when  struck  by  a hard  body.  It 
is  dull,  or  has  only  a feeble  lustre.  Its  colors  are  blackish -gray,  or  bluish-black, 
bluish,  or  reddish-brown,  or  greenish,  &c. 

It  belongs  both  to  secondary  and  primary  rocks.  Its  structure,  en  masse,  is 
tabular ; the  small  structure  lamellar ; the  cleavage  of  the  laminae  being  parallel 
with  the  tables. 

Slate  rocks  vary  in  hardness,  but  they  yield  to  the  knife.  They  consist  of  an 


OF  SLATE. 


27 


intimate  intermixture,  in  various  proportions,  of  siliceous  earth,  alumine,  and  iron  ; 
and  sometimes  contain  a portion  of  lime,  magnesia,  manganese,  and  bitumen. 
Slate  forms  entire  mountains,  and  sometimes  distinct  beds,  alternating  with  other 
rocks.  It  most  frequently  rests  on  granite,  gneiss,  and  mica-slate. 

As  this  substance  forms  the  most  light,  elegant,  and  durable  covering  for 
houses,  and  is,  of  course,  of  considerable  value,  it  is  rather  surprising  that  so 
much  indifference  prevails  respecting  the  search  for  it,  in  those  districts  where 
common  slate,  or  clay-slate,  abounds.  We  believe  all  the  roof-slate  quarries  at 
present  worked  are  those  which  accident  has  discovered.  This  neglect  is  the 
more  remarkable,  when  we  consider  the  great  expense  frequently  incurred  for 
coal,  a substance  of  less  value  in  proportion  to  the  weight. 

All  the  best  beds  of  roof-slate,  it  is  believed,  improve  as  they  sink  deeper  into 
the  earth ; and  few^,  if  any,  are  of  a good  quality  near  the  surface,  or  are  indeed 
suitable  for  the  purpose  of  roofing.  There  cannot  be  a doubt,  that  many  beds  of 
state,  which  appear  shattered  and  unfit  for  architectural  use,  would  be  found  of 
good  quality  a few  yards  under  the  surface ; for  the  best  slate,  in  many  quarries, 
loses  its  property  of  splitting  into  thin  laminae  by  exposure  to  the  air. 

Though  the  specific  gravity  of  slate  from  different  quarries  is  the  same,  yet  all 
the  sorts  are  not  capable  of  being  split  into  an  equal  degree  of  thickness.  It  is 
good  slate  which  will  split  into  laminae  of  one  eighth  of  an  inch  in  thickness.  It 
then  weighs  rather  more  than  twenty-six  ounces  to  a square  foot,  when  applied 
to  the  covering  of  a roof.  In  some  instances,  slate  of  a thinner  quality  is  used, 
where  cheapness  rather  than  durability  is  the  principal  object  of  the  architect. 
According  to  an  estimate  of  Dr  Watson,  the  relative  weights  of  a covering  of  the 
following  different  materials,  for  forty-two  square  yards  of  roof,  are,  — 

Copper,  - - 4 Cwt. 

Fine  Slate,  - 26  “ 

Lead,  - - 27  “ 

Coarse  Slate,  - 36  “ 

Tile,  - - 54  “ 

Slate,  to  be  of  a good  quality  for  building,  besides  possessing  the  property  of 
splitting  into  thin  laminae,  should  resist  the  absorption  of  water ; to  prove  whicn, 
it  should  be  kept  some  time  immersed  in  water,  being  weighed  before  and  after 
the  immersion,  wiping  the  surface  dry ; it  is  obvious  that  the  slate  which  gains 
the  least  weight  by  this  process  is  the  least  absorbent.  It  should  resist  the  pro- 
cess of  natural  decomposition  by  air  and  moisture  ; this  depends  on  its  chemical 
composition  and  compactness,  and  is  shown  by  its  resisting  the  process  of  vege- 
tation. That  slate  which  is  most  liable  to  decay,  will  be  the  soonest  covered 
with  lichens,  mosses,  &c.  The  hardness  of  slate  principally  arises  from  the  silex 


28 


PRACTICAL  MASONRY. 


it  contains,  which  is  of  all  earths  the  least  favorable  to  vegetation.  Those  slates 
which  are  the  hardest  when  first  taken  from  the  quarry,  and  which  have  the 
least  specific  gravity,  are  to  be  preferred ; for  the  increase  in  weight  is  owing  to 
the  presence  of  iron,  to  which  slate  and  other  stones,  in  some  measure,  owe 
their  decomposition  ; while  alumine  renders  them  soft  and  absorbent. 

Slate  is  so  durable,  in  some  cases,  as  to  have  been  known  to  continue  sound 
and  good  for  centuries.  However,  unless  it  should  be  brought  from  a quarry  of 
well  reputed  goodness,  it  is  necessary  to  try  its  properties,  which  may  be  done  by 
striking  the  slate  sharply  against  a large  stone,  and  if  it  produce  a complete  sound 
it  is  a mark  of  goodness ; but  if,  in  hewing,  it  does  not  shatter  before  the  edge  of 
the  instrument  commonly  used  for  that  purpose,  the  criterion  is  decisive.  The 
goodness  of  slate  may  be  farther  estimated  by  its  color  ; the  deep  blue-black 
kind  is  apt  to  imbibe  moisture,  but  the  lighter  blue  is  always  impenetrable.  The 
touch,  also,  in  some  degree,  may  be  a good  guide,  for  a good  firm  stone  feels 
somewhat  hard  and  rough,  whereas  an  open  slate  feels  very  smooth,  and,  as  it 
were,  greasy.  Another  method  of  trying  the  goodness  of  slate  is,  to  place  the 
slatestone  lengthwise  and  perpendicularly  in  a tub  of  water,  about  half  a foot 
deep,  care  being  taken  that  the  upper  or  unimmersed  part  of  the  slate  be  not 
accidentally  wetted  by  the  hand,  or  otherwise  ; let  it  remain  in  this  state  twenty - 
four  hours  ; and,  if  good  and  firm  stone,  it  will  not  draw  water  more  than  half  an 
inch  above  the  surface  of  the  water,  and  that,  perhaps,  at  the  edges  only,  those 
parts  having  been  a little  loosened  in  hewing ; but  a spongy,  defective  stone  will 
draw  water  to  the  very  top. 

Roof-slate  is  found  in  Pennsylvania,  on  the  banks  of  the  Delaware,  about  seven- 
ty-five miles  from  Philadelphia,  of  a good  quality.  In  New  York,  at  New  Paltz, 
Ulster  county ; and  at  Rhinebeck,  Duchess  county.  In  Dummerston,  Ver- 
mont, it  exists  in  strata  nearly  vertical ; it  is  also  found  at  Rockingham  and  Cas- 
tleton,  where  it  is  of  a pale  red.  It  exists  in  Maine,  at  Waterville  and  Winslow, 
on  the  Kennebec  River. 

Extensive  quarries  of  slate,  of  a good  quality,  are  worked  near  Bangor,  Eng- 
land ; this  slate  is  exported  in  large  quantities  to  various  parts  of  the  world. 

It  may  be  noticed,  that,  in  laying  of  this  material,  a bushel  and  a half  of  lime, 
and  three  bushels  of  fresh-water  sand, will  be  sufficient  for  a square  of  work;  but 
if  it  be  pin-plastered,  it  will  take  about  as  much  more ; but  good  slate,  well  laid 
and  plastered  to  the  pin,  will  lie  a hundred  years,  and  on  good  timber  a much 
longer  time.  It  has  been  common  to  lay  the  slates  dry,  or  on  moss  only,  but 
they  are  much  better  when  laid  with  plaster. 


OF  SOAPSTONE,  OR  STEATITE. 


29 


SECTION  XII.  — Soapstone,  or  Steatite. 

All  the  varieties  of  soapstone  are  so  soft,  that  they  may  be  cut  by  a knife, 
and,  in  most  cases,  scratched  by  the  finger-nail.  Its  powder  and  surface  are  soft, 
and  more  or  less  unctuous  to  the  touch.  It  is  seldom  translucent,  except  at  the 
edges.  Its  fracture  is  in  general  splintery,  earthy,  or  slaty,  with  little  or  no 
lustre. 

By  exposure  to  the  heat  it  becomes  harder,  but  is  almost  infusible  by  the  blow- 
pipe. It  appears  to  be  essentially  composed  of  silex,  magnesia,  and  perhaps 
alumine. 

The  common  variety  is  usually  solid,  with  a compact  texture  ; its  surface  is 
often  like  soap  to  the  touch  ; but  sometimes  it  is  found  of  a considerable  degree 
of  hardness. 

Its  color  is  usually  gray  or  white,  seldom  pure,  but  occasionally  mixed  with 
yellow,  green,  or  red,  and  is  sometimes  a pale  yellow,  reddish,  or  green  of  different 
shades.  The  colors  sometimes  appear  in  spots,  veins,  &c. 

Its  specific  gravity  usually  lies  between  2.58  and  2.79.  When  solid  it  is 
somewhat  difficult  to  break.  Before  the  blow-pipe  it  whitens  and  becomes  hard, 
and  is  with  difficulty  reduced  into  a whitish  paste  or  enamel,  often,  however,  only 
at  the  extremity  of  the  fragment.  Some  specimens  have  yielded  by  analyzation, 
silex  64  parts,  magnesia  22,  alumine  3,  water  5,  iron  and  manganese  5. 

Soapstone  occurs  in  masses,  or  veins,  or  small  beds,  in  primitive  and  transition 
rocks,  more  particularly  in  serpentine.  It  is  sometimes  mixed  with  talc,  mica, 
quartz,  and  asbestos ; or  is  found  incrusted  with  other  minerals. 

This  stone  is  not  uncommon.  It  is  found  in  various  parts  of  the  United  States. 
Among  the  best  quarries  for  fire-proof  stone  is  that  of  Francestown,  New  Hamp- 
shire. It  occurs,  also,  in  Connecticut,  near  New  Haven,  and  at  Oxford,  Grafton, 
and  Athens,  in  Vermont. 

Soapstone,  on  account  of  its  softness,  is  wrought  with  the  same  tools  as  wood. 
It  receives  a tolerable  polish,  and  is  sometimes  used  in  building,  but  is  not  always 
durable.  It  is,  however,  of  great  importance  in  the  construction  of  fire-places  and 
stoves,  and  is  extensively  used  for  this  purpose.  Slabs  of  good  soapstone,  when 
not  exposed  to  mechanical  injury,  frequently  last  eight  or  ten  years,  under  the 
influence  of  a common  fire  on  one  side,  and  of  cold  air  on  the  other.  It  grows 
harder  in  the  fire,  but  does  not  readily,  crack,  nor  change  its  dimensions  suffi- 
ciently to  affect  its  usefulness.  Owing  to  the  facility  with  which  it  is  wrought,  its 
joints  may  be  made  sufficiently  tight  without  dependence  on  cement. 


30 


PRACTICAL  MASONRY. 


It  is  often  wrought  into  various  utensils  by  turning,  and  is  advantageously 
employed  for  aqueducts.  It  has  been  found  to  be  one  of  the  best  materials  for 
• counteracting  friction  in  machinery,  for  which  purpose  it  is  used  in  powder,  mixed 
with  oil.  It  has  also  been  employed  for  the  purpose  of  engraving.  By  being 
easily  cut,  when  soft,  it  may  be  made  to  assume  any  desired  form,  and  afterwards 
rendered  hard  by  heat ; it  then  becomes  susceptible  of  a polish,  and  may  be 
variously  colored  by  metallic  solutions. 


SECTION  XIII.  — Gypsum. 

Gypsum  is  a term  applied  in  its  restricted  sense  to  those  varieties  of  sulphate 
of  lime  which  have  a fibrous  or  granular  structure,  being  the  result  of  confused 
crystallization,  and  to  those,  whose  texture  is  compact,  or  earthy.  It  is  a sub- 
stance that  is  interesting  on  account  of  its  uses  in  agriculture  and  the  arts.  Its 
colors  are  commonly  white  or  gray,  sometimes  shaded  with  yellow,  red,  or  vari- 
ously mingled. 

It  occurs  in  compact  masses,  sometimes  granular,  and  sometimes  in  parallel 
fibres.  Though  sometimes  coarse,  the  fibres  are  often  fine  and  delicate,  glisten- 
ing with  a pearly  satin  lustre.  Its  fracture  is  foliated,  sometimes  splintery ; it  is 
generally  translucent,  often  in  amorphous  masses  ; but  not  unfrequently  crystal- 
lized. It  is  less  hard  than  carbonate  of  lime.  Its  specific  gravity  usually  lies 
between  2.26  and  2.31.  By  the  blow-pipe  it  may  be  melted,  though  not  very 
easily,  into  a white  enamel,  which  shortly  falls  into  a powder.  It  does  not  effer- 
vesce with  acids,  if  it  be  pure  sulphate  of  lime.  It  is  soluble  in  about  five  hun- 
dred times  its  weight  of  water.  It  does  not  bum  to  lime. 

It  is  composed  of  32  parts  of  lime,  46  of  sulphuric  acid,  and  22  parts  of  water ; 
but  it  is  often  contaminated  with  small  quantities  of  carbonate  of  lime,  alumine, 
silex,  and  oxyd  of  iron.  Some  varieties  are  employed  in  sculpture  and  architec- 
ture under  the  name  of  alabaster ; the  same  name  is  also  given  to  some  varieties 
of  carbonate  of  lime. 

The  plaster-stone,  or  plaster  of  Paris,  often  contains  foreign  ingredients,  which, 
in  many  instances,  improve  it  as  a cement. 

This  substance  is  found  in  abundance  in  many  places,  and  has  been  extensively 
used  for  manure  in  dressing  land,  and  appears  to  be  useful  in  both  clayey  and 
sandy  soils.  It  is  also  employed  in  the  imitative  and  ornamental  arts.  Alabaster, 
both  of  the  sulphate  and  carbonate  kinds,  has  been  used  for  the  same  purposes 
as  marble  in  architecture  and  statuary  ; and,  being  less  hard,  it  is  more  easily 
wrought ; but  is  less  durable  and  less  valuable  than  marble.  Gypsum,  when 


OF  PUZZOLANA. 


31 


deprived  of  its  water  of  crystallization  by  burning  or  drying,  constitutes  plaster, 
and  this  plaster,  when  mixed  with  a certain  quantity  of  quicklime,  forms  a good 
cement.  The  plaster  of  Paris  often  contains,  in  its  natural  state,  a sufficient 
quantity  of  carbonate  of  lime  to  constitute  a good  cement  after  calcination. 

The  finer  kinds  of  plaster,  being  reduced  to  powder,  and  mixed  with  water, 
have  the  property  of  becoming  hard  in  a few  minutes,  and  of  receiving  accu- 
rately the  impressions  of  the  most  delicate  models.  It  is  extensively  employed  in 
stucco  work,  and  in  plastering  rooms.  It  furnishes  a delicate,  white,  and  smooth 
material  for  architectural  models,  impressions  of  seals,  &.c. ; and  in  the  art  of 
stereotyping  it  is  indispensable.  In  stucco,  various  colors,  previously  ground  in 
water,  may  be  introduced.  All  these  works,  when  dry,  are  susceptible  of  a 
polish. 

The  Temple  of  Fortune,  called  Seja,  appears  to  have  been  built  with  some 
variety  of  sulphate  of  lime.  It  had  no  windows,  but  transmitted  a mild  light 
through  its  walls. 


SECTION  XIV.  — PvzzoLANA. 

This  substance  is  of  volcanic  origin.  It  usually  occurs  in  small  fragments,  or 
friable  masses,  which  have  a dull,  earthy  aspect  and  fracture,  and  seems  to 
have  been  baked.  Its  solidity  does  not  exceed  that  of  chalk.  It  is  seldom 
tumefied,  and  its  pores  are  neither  large  or  numerous.  Its  colors  are  gray  or 
whitish,  reddish  or  nearly  black. 

By  exposure  to  the  heat  it  melts  into  a black  slag.  A variety  examined  by 
Bergaman  yielded  55  to  60  parts  of  silex,  19  to  20  of  alumine,  15  to  20  of  iron, 
and  5 to  6 parts  of  lime.  It  often  contains  distinct  particles  of  pumice,  quartz, 
and  scoria. 

This  substance  is  extremely  useful  in  the  preparation  of  a mortar  which  hardens 
quickly,  even  under  water.  When  thus  employed  it  is  mixed  with  a small  pro- 
portion of  lime,  perhaps  one  third.  It  has  been  supposed  that  the  rapid  indura- 
tion of  this  mortar  arises  from  the  very  low  oxydation  of  the  iron.  If  the  mortar 
be  a long  time  exposed  to  the  air,  previous  to  its  use,  it  will  not  harden.  The 
best  puzzolana  is  said  to  occur  in  old  currents  of  lava ; but  when  too  earthy  it 
loses  its  peculiar  properties.  That  which  comes  from  Naples  is  generally  gray. 


32 


PRACTICAL  MASONRY. 


SECTION  XV.  — Tras,  or  Terras. 

The  nature  of  this  is  similar  to  some  varieties  of  puzzolana ; and  it  contains 
nearly  the  same  principles,  but  with  a greater  proportion  of  lime.  Its  hardness 
is,  however,  much  greater  than  that  of  puzzolana.  Its  color  is  brownish  or  yel- 
lowish ; and  its  fracture  earthy  and  dull.  It  has  been  found  chiefly  near  Ander- 
nach,  in  the  vicinity  of  the  Rhine. 

It  is  said  to  be  decomposed  basalt.  It  forms  a durable  water-cement  when 
combined  with  lime.  It  is  the  material  which  has  been  principally  employed  by 
the  Dutch,  whose  aquatic  structures  probably  exceed  those  of  any  other  nation 
in  Europe.  Terras  mortar,  though  very  durable  in  water,  is  inferior  to  the  more 
common  kinds,  when  exposed  to  the  open  air. 


SECTION  XVI.  — Quarrying. 


The  common  methods  of  working  and  managing  different  sorts  of  quarries  are 
in  general  pretty  well  understood  by  such  quarrymen  as  are  constantly  employed 
in  the  business.  The  materials  are  indicated  by  the  appearance  of  the  surface  of 
the  earth,  the  nature  of  the  substances  in  the  vicinity,  or  by  digging  down  and 
opening  the  ground  by  spades  and  other  tools,  or  by  boring  with  an  auger  made 
for  the  purpose. 

The  great  value  to  mankind  of  such  materials  as  coal,  iron  ores,  &c.,  as  well 
as  of  building  materials,  should  induce  proprietors  of  land  to  cause  a more  diligent 
and  scientific  search  for  these  hidden  treasures  than  has  been  hitherto  practised 
in  this  country.  It  may  also  be  suggested,  that  it  would  be  highly  beneficial  and 
advantageous,  if  mineralogists  and  those  who  have  an  acquaintance  with  such 
substances  were  to  turn  their  attention  towards  the  appearances  and  accompani- 
ments which  point  out  such  useful  concealed  matters  ; as  it  might  greatly  facili- 
tate the  search  for  them,  and  frequently  lead  fortuitously  to  their  discovery.  In 
searching  for  most  sorts  of  mineral  substances,  coals,  and  some  other  matters,  the 
use  of  the  borer  is  almost  constantly  resorted  to ; but  with  regard  to  limestone, 
freestone,  granite,  &.C.,  digging  down  into  the  earth  is  the  mode  commonly  em- 
ployed in  the  first  instance,  in  consequence  of  such  substances  being  obviously 
present  in  sufficient  quantities  to  be  wrought  with  advantage. 

When  it  has  been  ascertained  that  the  material  exists  in  sufficient  quantity  to 


OF  QUARRYING. 


33 


warrant  the  working  of  the  quarry,  much  time  and  expense  will  be  saved  by  pro- 
ceeding in  a correct  manner  in  the  first  opening  of  it. 

Instead  of  beginning  to  dig  at  the  top,  by  which  means  the  progress  of  the 
workmen  will  soon  be  impeded  by  accumulating  rubbish,  or  the  rushing  in  of 
water,  it  would  be  far  preferable  to  commence  on  one  side  of  the  elevation  which 
contains  the  material,  having  previously  ascertained  which  way  the  rocks  incline 
or  dip,  and  gradually  approach  the  quarry  on  this  side ; clearing  away  the  dirt 
and  superincumbent  substances  as  low  down  as  the  nature  of  the  ground  will 
admit.  In  this  manner,  the  mouths  or  openings  of  the  quarries  may  be  easily 
kept  free,  and  the  water  carried  off ; at  the  same  time,  the  materials  may  be  op- 
erated upon  and  removed  with  the  greatest  facility.  If  the  nature  of  the  situa- 
tion admits  of  the  opening  of  a quarry  in  this  manner,  the  more  convenient  method 
of  working  it  is  by  gradations  or  steps.  That  is,  the  stone  is  first  taken  from  the 
top  to  an  uniform  depth,  for  a considerable  distance  back ; then  another  stratum 
or  layer  is  removed,  till  it  approaches  within  some  distance  of  the  first,  when  a 
third  is  begun,  and  so  on  ; so  that  the  quarry  presents  the  appearance  of  steps, 
or  horizontal  planes  one  above  the  other.  This  method  affords  facilities  for  re- 
moving the  stone  or  materials,  without  the  aid  of  expensive  machinery. 

There  is  often  a great  difference  in  the  quality  of  the  material  in  the  same 
quarry.  Those  portions  which  are  nearest  to  the  surface  are  sometimes  mixed 
with  foreign  ingredients,  that  impair  their  value  or  render  them  useless. 

The  stones  are  obtained  of  suitable  dimensions  by  blasting,  by  splitting  with 
iron  wedges  set  in  a direct  line,  and  driven  with  much  force  by  a sledge  or  ham- 
mer. Advantage  is  often  taken  of  natural  fissures  which  are  in  straight  lines,  and 
often  at  right  angles. 

Granite,  and  the  stones  related  to  it,  although  of  great  hardness,  will  split  very 
straight,  by  means  of  wedges.  The  pieces  are  afterwards  wrought  into  the  form 
to  be  used,  either  at  the  quarry,  which  diminishes  the  expense  of  transportation, 
or  removed  in  a rough  state,  and  thus  used  in  building  ; or  finished,  as  may  be 
deemed  expedient. 

In  working  granite  and  materials  of  a similar  nature,  it  is  first  lined,  or  marked 
into  the  form  desired.  The  workman  then  forms  the  edge  all  round  by  means 
of  a chisel  and  hammer,  making  it  smooth  and  straight  to  the  depth  of  one  or  two 
inches  ; he  afterwards  breaks  off  the  larger  portions  with  a hammer  made  in  a 
peculiar  form,  and  kept  sharp  ; with  this  instrument  he  continues  to  take  off  the 
inequalities  of  the  surface,  till  it  has  the  requisite  smoothness. 

Sandstone,  freestone,  and  materials  of  the  like  nature,  being  less  hard  than 
granite,  are  more  easily  wrought  by  a similar  process.  Some  of  them  admit  of  a 
considerable  degree  of  polish. 


5 


34 


PRACTICAL  MASONRY. 


Marble  and  soapstone  are  taken  from  the  quarries  in  large  masses,  and  after- 
wards sawed,  either  by  hand,  or  in  mills  constructed  for  the  purpose,  and  then 
polished.  (See  Marble  and  Soapstoiie.)  Slate,  in  some  instances,  is  obtained 
by  blasting.  It  is  sometimes  dug  out  by  one  set  of  men,  split  by  another,  and 
formed  into  slates  by  a third  ; for  which  purposes,  flat  crowbars,  slate-knives, 
and  axes  are  employed.  It  is  often  divided  into  three  sorts,  as  firsts,  seconds, 
and  thirds,  which  vary  in  quality  and  price. 

Sand  and  gravel  are  mostly  dug  out  from  the  sides  of  banks,  and  other  places ; 
and  but  rarely  obtained  by  sinking  the  quarries  into  the  more  level  parts  of  the 
ground,  though  this  method  is  sometimes  practised,  d'he  materials  are  common- 
ly raised,  simply  by  digging  with  spades  ; and  thrown  into  carts,  in  many  cases, 
from  the  quarries  or  pits  themselves. 

The  removal  of  materials  from  quarries  is  effected  by  means  of  inclined  planes, 
of  railways,  or  by  various  machines  constructed  for  the  purpose,  such  as  the 
windlass,  the  pulley,  &c.,  adapted  in  each  instance  to  the  situation  of  the  quarry, 
and  the  circumstances  of  the  case. 

The  Quincy  stones  are  raised  from  their  beds  by  the  means  of  a windlass 
worked  by  a horse,  and  received  upon  cars,  which  run  upon  inclined  railways, 
within  a few  feet  of  the  quarry  ; from  thence  they  are  conveyed  to  the  sea  on  a 
railway,  and  transported  in  various  directions.  By  the  descent  of  a loaded  car 
on  the  inclined  railway  at  the  quarry,  an  empty  car  is  drawn  up. 

' The  greatest  difficulty  incident  to  working  quarries  is  that  of  draining,  and 
freeing  their  bottom  parts  from  injurious  water  ; so  that  they  may  be  in  a fit  state 
to  be  wrought  with  ease  and  advantage. 

The  most  usual  remedies  resorted  to  in  this  difficulty  are  pumps  worked  by 
wind,  by  horse,  steam,  or  other  powers ; but  these  often  prove  ineffectual  in  re- 
moving the  water  completely,  and  new  quarries  are  opened  near  the  old  ones. 
But  an  attention  to  certain  principles,  in  regard  to  the  nature  of  the  soil  and  the 
courses  of  subterraneous  waters,  may  often  lead  to  more  cheap,  expeditious,  and 
effectual  remedies. 

It  is  now  well  understood,  that  most  springs  and  subterraneous  collections  of 
Avater  are  formed  and  supplied  from  such  grounds  as  lie  higher  than  that  of  the 
places  where  the  waters  are  met  with,  which,  in  consequence  of  their  being  of  an 
open  and  porous  nature,  admit  the  rain  and  other  sorts  of  moisture  to  filtrate  and 
pass  freely  through  them.  These  waters  descend  to  great  depths  before  they 
become  impeded  by  some  sort  of  impenetrable  stratum,  or  layer  of  a solid  or  siony 
nature,  as  clay,  or  compact  rock.  It  may  happen,  in  sinking  quarries,  that  beds 
of  quicksand  may  be  met  with,  which  are  so  full  of  water,  that  to  penetrate 
through  them  will  be  very  difficult ; and  from  a knowledge  that  the  water  pro- 


OF  QUARRYING. 


35 


ceeds  from  the  porous  ground  that  lies  above  them,  it  may  be  practicable  to  in- 
tercept and  cut  off  the  greater  part  of  it  before  it  reaches  the  sand-beds  in  the 
quarries,  by  the  means  of  boring  into  and  tapping  the  water  at  the  tails  of  the 
banks  of  this  nature,  provided  that  the  ground  declines  lower  than  the  place 
where  the  sand  is  found  in  the  quarries,  which  may  be  done  at  a trifling  expense 
in  comparison  to  the  common  remedies. 

But  in  order  to  accomplish  this  intention,  it  will  be  necessary,  in  ascending  from 
the  quarry,  to  ascertain  if,  at  the  place  higher  on  the  declivity,  any  porous  stratum, 
bed  of  rock,  sand,  or  gravel,  tails  out,  which  may  convey  the  water  contained  in 
it  to  the  sand-bed,  which  is  below  in  the  works  ; and  where  any  such  is  found, 
to  cut  and  bore  into  it,  in  such  a manner  as  to  form  a drain,  that  is  capable  of 
conveying  off  the  water,  which  would  otherwise  have  descended  into  the  quarry. 

But  although  this  part  of  the  business  may  have  been  accomplished,  and  the 
supply  of  water  from  the  higher  ground  entirely  cut  otf,  a sufficient  quantity  to 
injure  and  inconvenience  the  working  may  yet  continue  to  drain  from  the  sides  of 
the  sand-beds,  though  they  should  happen  to  dip  towards  the  lower  ground ; in 
which  cases,  however,  this  water  may  be  drawn  off  readily  to  some  particular 
point. 

In  order  to  effect  this,  it  should  be  ascertained  at  what  particular  place  in  the 
low  ground  the  sand  terminates,  or  tails  out,  which  is  the  best  accomplished  by 
means  of  proper  levelling  ; and  if  there  should  be  any  appearance,  in  this  place, 
of  the  water’s  having  a natural  outlet,  it  may,  by  making  it  into  a deep  drain, 
cause  the  water  effectually  to  be  drawn  off.  Where,  however,  there  happens  to 
be  a deep,  impervious  layer  of  clay,  or  other  matter  of  a similar  nature,  placed 
above  or  upon  the  termination  or  tail  of  the  sand,  the  drain  need  only  be  cut 
down  to  it,  or  a little  way  into  it,  as  by  means  of  boring  through  it  a ready  and 
easy  passage  may  be  given  to  the  whole  of  the  water  contained  in  the  sand-bed 
or  porous  stratum. 

It  is  of  material  importance  to  lay  dry  all  such  grounds  as  are  situated  higher, 
but  contiguous  to  quarries,  for  the  above-stated  reasons ; and  it  may  in  general 
be  accomplished  with  but  little  difficulty  and  expense,  by  adopting  the  same 
principles  and  the  same  means. 

This  is  the  mode  that  is  to  be  pursued  in  preventing  the  effects  of  the  water, 
or  cutting  it  off,  when  met  with  in  sinking  quarries.  It  proceeds  on  the  principle 
of  the  dipping  position  of  the  strata,  with  I he  natural  inclination  of  the  land. 

It  frequently  happens  that  a body  of  the  same  stone,  which  is  of  a close  and 
compact  nature,  is  found  lying  under  one  which  has  a more  open  and  porous 
texture,  with  fissures  and  cracks  in  it,  that  are  admissible  of  water,  in  the  upper 
body  or  layer,  in  such  a manner  that  none  can  pass  through  it  to  the  inferior,  or 


36 


PRACTICAL  MASONRY. 


Still  deeper,  open  stratum  or  bed ; and  on  sinking  or  cutting  through  this  compact 
bed,  another  layer  is  met  with,  which  is  of  so  porous  a nature  as  to  admit  the  re- 
ception of  any  water  that  may  come  upon  it.  And  sometimes  a bed  of  gravel  or 
sand  is  found  under  that  of  close  stone,  which,  being  capable  of  absorbing  any 
water  that  may  come  upon  it,  is  far  better  suited  for  the  purpose  of  clearing  the 
upper  bed  of  stone  from  water  than  the  stratum  of  open  stone  itself.  Therefore, 
when  this  is  ascertained  to  be  the  case,  and  the  water  is  kept  up  by  the  second 
bed  of  stone,  so  as  to  be  injurious  to  the  working  of  the  upper  bed,  and  which 
will  be  equally  so  in  working  the  second,  the  work  may  be  greatly  freed  by  bor- 
ing through  the  close  bed  of  stone,  and  letting  the  water  down  into  the  more 
porous  one  below,  or  into  a stratum  of  dry  sand  or  gravel,  should  there  be  such  a 
one  underneath  it.  But,  instead  of  boring,  the  sinking  of  small  pits  through  the 
close  stone  is  a more  effectual  way  of  letting  down  the  water. 

In  all  such  cases  as  these,  boring  or  sinking  pits  through  the  solid  stratum  into 
a porous  substance  or  layer  underneath  is  the  most  advisable,  and,  at  the  same 
time,  the  least  expensive,  method  that  can  be  pursued. 


OF  THE  WEIGHT  OF  STONE. 


37 


TABLE. 

The  following  table  shows  the  weight  of  granite  stone,  in  pounds  and  hundredths,  both  in  a cubi- 
cal and  cylindrical  form  ; the  dimensions  being  given.  The  first  column  of  figures  denotes  a piece 
of  stone  to  be  1,2,3,  &c.,  inches  square,  or  in  diameter;  each  piece  being  12  inches  in  length. 
Columns  two  and  three  are  the  mean  weight  of  common  stone  ; four  and  five,  the  weight  of  the 
Quincy  stone ; six  and  seven,  the  weight  of  a species  of  coarse  granite,  found  at  Sandy  Bay,  in 
Massachusetts. 


MEAN  WEIGHT  OF  STONE  IN  GENERAL. 

QUINCV  GRANITE. 

S.VNDV  BAY 

GRANITE. 

Square. 

C>lindric. 

Siiuare. 

Cylindric. 

Square. 

Cylindric. 

. 

" 1 

1.07 

.86 

1.16 

.95 

1.17 

.95 

to 

2 

4.33 

3.45 

4.65 

3 80 

4.68 

3.80 

-2 

3 

9.70 

7.75 

10.44 

8.55 

10  53 

8.56 

' o 

4 

17.33 

13.80 

18.56 

15.20 

18.72 

15.21 

5 

27.00 

21.50 

29.00 

i o 

29.22 

23.77 

6 

38.10 

31.00 

41.76 

34.20 

42. 12 

34.23 

7 

52.67 

42.00 

55.88 

46.55 

57.33 

T4.59 

1 » 

8 

69.00 

55.00 

74.24 

60.80 

74.88 

60.86 

! 1 

9 

86.67 

69.65 

83.96 

76.95 

94.77 

77.03 

5 

10 

107.33 

86.00 

116.00 

95.00 

117.00 

95.10 

11 

130.00 

104.00 

140..36 

114.95 

141.57 

115.07 

1 ^ 

1 

12 

- 

155.00 

124.00 

167.04 

136.80 

168.48 

136.94 

1 tb 

' 1 

5.35 

4.30 

5.80 

4.75 

5.85 

4.75 

1 o 

2 

23.65 

17.25 

23.20 

19  00 

23.40 

19.40 

3 

48.50 

38.75 

52.20 

42.75 

52.65 

42.80 

1 o 

o 

4 

86.65 

69.00 

92.80 

76.00 

93.60 

75.05 

5 

135.00 

107.. 50 

145.00 

118.75 

146.10 

118.85 

6 

190.50 

155.00 

200.80 

171.00 

210.00 

171.15 

1 t ^ 

7 

263.35 

310.00 

379.20 

232.75 

286.65 

222.95 

8 

345.00 

275.00 

1 371.20 

304.00 

374.40 

304.30 

o 

9 

433.35 

318.00 

419.80 

38475 

1 473.85 

385.15 

1 c 

10 

536.65 

430.00 

580.00 

475  00 

1 585.00 

475.50 

1 

11 

650.00 

520.00 

701.80 

574.75 

j 707.85 

575.35 

; ” 

775.00 

620.00 

835.20 

680  00 

! 842.10 

1 

684  70 

' 1 

10.70 

8.60 

11.60 

9.50 

11.70 

9.50 

j « 

2 

43  30 

34..50 

46.40 

38.00 

56.80 

38.00 

O 

3 

97.70 

77.50 

104.40 

85.50 

10530 

85.60 

o 

4 

173.30 

138.00 

185.60 

152.00 

187.20 

152.10 

5 

270.00 

215.00 

290.00 

237.50 

292.20 

237.70 

o 

6 

381.00 

310.00 

417.60 

342.00 

i 421.20 

342.30 

1 cS 

7 

526.70 

420.00 

558.40 

465.50 

, 573.30 

445.90 

8 

690.00 

550.00 

742.40 

608.00 

1 748.80 

608.60 

o 

9 

866.70 

696.00 

839.60 

769.50 

1 947.70 

770.30 

10 

1073.00 

860.00 

1160.00 

950.00 

i 1 170.00 

951.00 

i 0? 

11 

1.300.00 

1040.00 

1403.00 

1149.00 

1415.70 

11.50.70 

i ^ 

.12 

1550.50 

1240.00 

1670.40 

1368.00 

1684.80 

1369.40 

38 


PRACTICAL  MASONRY. 


Mean  Weight  of  a Cubic  Foot  of  Stone,  and  the  Weight  it  w sustain  with  Safety. 


Granite. 

Mean  Weight. 

Weight  it  will  sustain. 

Sandy  Bay  Stone, 

148.48  lbs. 

197,000  lbs. 

Quincy  do. 

167.04  “ 

156,000  “ 

Concord  do. 

159.00  “ 

149,000  “ 

Frankfort  do. 

162.00  “ 

148,000  “ 

Marble. 

White  New  York, 

173  lbs. 

85,000  lbs. 

New  Haven  Variegated, 

175  “ 

89,000  “ 

Pennsylvania  Dove, 

170  “ 

86,000  “ 

Thomaston  Blue, 

179  “ 

90,000  “ 

Vermont  Dove, 

168  “ 

86,000  “ 

Sandstone  or  Freestone. 

Connecticut, 

164  lbs. 

118,000  lbs. 

North  River, 

156  “ 

108,000  “ 

Potomac, 

153  “ 

98,000  “ 

TABLE  OF  CYLINDRICAL  MEASURES. 

Designed  for  the  computation  of  the  contents  of  lead  pipes,  from  one  inch  diameter  to  three  and 
upwards ; also,  cisterns  of  ten  feet  diameter  and  under ; the  quantity  and  weight  of  water  in 
pumps,  suction  pipes,  &c.,  from  one  inch  diameter  and  upwards. 


Inches  Diame- 
ter. 

Cubic  feet  and  parts. 

Ale  gallons  and  parts. 

Wine  gallons  and 
parts. 

Weight  of  water,  in  lbs. 
and  parts. 

Dry  bushels  and  parts. 

1 

.0055 

.033 

.04 

.34 

.0044 

2 

.0218 

.134 

.16 

1.36 

.0175 

3 

.0491 

.301 

.37 

3.06 

.0394 

4 

.0873 

.534 

.65 

5.45 

.0700 

5 

.136 

.835 

1.02 

8.52 

.110 

6 

.196 

1.20 

1.47 

12.27 

.158 

7 

.267 

1.64 

2.00 

16.70 

.215 

8 

.349 

2.14 

2.61 

21.82 

.281 

9 

.442 

2.71 

3.30 

27.61 

.355 

10 

.545 

3.34 

4.08 

34.09 

.438 

11 

.660 

4.04 

4.94 

41.25 

.530 

12 

.785 

4.81 

5.88 

49.09 

.631 

24 

3.14 

19.25 

23.52 

196.36 

2.521 

36 

7.07 

43.30 

52.92 

441.79 

5.68 

48 

12.57 

77.00 

94.08 

785.44 

10.10 

50 

13.64 

83.55 

102.00 

852.21 

11.00 

60 

19.64 

120.30 

146.88 

1227.19 

15.78 

72 

28.28 

173.20 

211.51 

1767.15 

22.72 

84 

38.49 

235.81 

287.88 

2405.28 

30.92 

96 

50.27 

308.00 

376.01 

3141.59 

40.39 

108 

63.62 

389.79 

475.89  t 

3976.08 

51.12 

120 

78.54 

481.25 

587.52 

4903.74 

63.11 

N.  B.  If  the  diameter  should  fall  between  any  of  the  numbers  in  the  first  column,  the  mean 
proportional  contents  may  be  found  by  adding  the  two  contents  between  which  it  falls,  and  dividing 


OF  THE  WEIGHT  OF  IRON. 


39 


by  two.  Suppose  it  falls  between  108  and  120  of  the  diameters,  required  the  wine  gallons  in  114 

inches,  or  9 feet  6 inches  diameter,  which  falls  between  587.52 

and  475.89 

2)1063.41 

Answer,  531.70| 

Or  if  between  60  and  72,  say  64  inches,  or  5 feet  4 inches  ; one  third  of  12  is  4 ; then  required 

the  cubic  feet  and  parts. 

28.28 

Subtract  19.64 
Divide  by  3)  8.64 

Add  19.64 
Answer,  22.52 

Any  depth  may  be  found,  by  multiplying  by  the  depth  any  of  the  numbers  in  the  contents  ; as,  re- 
quired the  number  of  ale  gallons  in  24  inches  diameter,  at  6 feet  deep.  19.25  X 6 — 115.50,  Ans. 


A TABLE 

For  the  computation  of  the  weight  of  wrought  iron  of  different  dimensions,  from  ^ of  an  inch  to 
5 inches  square  ; also,  round,  from  ^ of  an  inch  to  5 inches  diameter.  The  third  and  fourth  columns 
for  flat  bars,  from  1^  to  6 inches  wide,  from  ^ to  5 inches  thick  ; each  dimension  estimated  at  one 
foot  in  length. 


Square  Bars. 

! 

Round  Iron. 

Flat  Bars. 

In. 

8lhs. 

lbs. 

OZ. 

dr.  1 

In. 

Sths. 

lbs. 

OZ. 

dr. 

In.  Sths. 

lbs. 

OZ. 

dr. 

In.  Sths. 

lbs. 

OZ. 

dr. 

1 

0 

1 

12  i 

1 

0 

0 

14 

l|Xl 

0 

4 

6 

2|X2 

2 

3 

0 

2 

0 

3 

8 1 

2 

0 

1 

12 

2 

0 

8 

12 

3 

3 

4 

8 

3 

0 

7 

14  ! 

3 

0 

7 

0 

3 

1 

10 

4 

4 

4 

6 

0 

4 

0 

14 

0 ' 

4 

0 

11 

0 

4 

2 

3 

0 

5 

5 

7 

8 

5 

1 

5 

14 

5 

1 

1 

3 

5 

2 

11 

12 

6 

6 

9 

0 

6 

1 

15 

8 

6 

1 

8 

12 

HX2 

1 

5 

0 

7 

7 

10 

8 

7 

2 

10 

14 

7 

2 

1 

11 

3 

1 

15 

8 

8 

8 

12 

0 

1 

0 

3 

8 

0 

1 

0 

2 

12 

0 

4 

2 

11 

0 

2|X3 

3 

9 

12 

1 

4 

6 

14 

1 

3 

7 

11 

5 

3 

4 

8 

4 

4 

13 

0 

2 

5 

7 

8 

2 

4 

4 

12 

1|X2 

1 

8 

8 

5 

6 

0 

4 

3 

6 

9 

14 

3 

5 

3 

3 

3 

2 

4 

12 

6 

7 

3 

8 

4 

7 

14 

0 

4 

6 

3 

0 

4 

3 

1 

0 

7 

9 

10 

0 

5 

9 

3 

14 

5 

7 

4 

3 

5 

3 

13 

4 

3x3 

3 

15 

0 

6 

10 

11 

8 

6 

8 

6 

12 

6 

4 

9 

8 

4 

5 

4 

0 

7 

12 

4 

14 

7 

9 

10 

11 

7 

5 

5 

12 

5 

6 

9 

0 

2 

0 

14 

0 

0 

2 

0 

11 

0 

0 

8 

6 

2 

0 

4x3 

5 

4 

0 

1 

15 

12 

14 

1 

12 

6 

11 

2 X2 

1 

12 

0 

4 

7 

0 

0 

2 

17 

11 

8 

2 

13 

14 

12 

3 

2 

10 

0 

5 

8 

12 

0 

4 

21 

14 

0 

3 

15 

8 

3 

4 

3 

8 

0 

8 

14 

0 

0 

6 

26 

7 

8 

4 

17 

3 

0 

5 

4 

6 

0 

5x3 

6 

9 

0 

3 

0 

34 

0 

0 

5 

18 

15 

3 

6 

5 

4 

0 

4 

8 

12 

0 

2 

36 

15 

8 

6 

20 

12 

12 

7 

6 

2 

0 

5 

10 

15 

0 

4 

42 

14 

0 

7 

22 

11 

11 

8 

7 

0 

0 

6 

13 

2 

0 

6 

49 

3 

8 

3 

0 

24 

12 

0 

2|X2 

1 

15 

8 

6X3 

7 

14 

0 

4 

0 

54 

0 

0 

4 

0 

44 

0 

0 

3 

2 

15 

4 

4 

10 

8 

0 

2 

63 

2 

8 

2 

49 

11 

12 

4 

3 

15 

0 

5 

13 

2 

0 

4 

70 

14 

0 

1 5 

0 

68 

12 

0 

5 

4 

14 

12 

6 

78 

15 

8 

1 

1 

5 

0 

87 

8 

0 

40 


PRACTICAL  MASONRY. 


RULES 

FOR  MEASURING  HAMMERED  GRANITE  STONE, 
ADOPTED  APRIL,  1829. 


PREAMBLE. 

To  prevent  misunderstanding  between  the  stonecutters,  the  masons,  and  their  employers,  in 
relation  to  the  admeasurement  of  hammered  granite  stone,  it  was  deemed  expedient  that  a meet- 
ing be  called  of  those  engaged  in  the  business,  to  endeavour  to  agree  upon  some  uniform  system, 
that  shall  be  equally  intelligible  to  all  parties  ; said  meeting  was  held  in  March  last,  when  a com- 
mittee of  eleven  persons  was  chosen,  to  take  the  subject  into  consideration,  and  report  at  a subse- 
quent meeting.  At  a meeting  in  April,  said  committee  reported,  that  they  had  attended  to  the 
duty  assigned  them,  and,  after  mature  deliberation,  have  agreed  on  the  following  rules,  which,  if 
adopted,  will,  in  their  opinion,  greatly  promote  the  interest  as  well  as  the  harmony  of  all  concerned 
in  the  business,  whether  purchaser  or  vender  ; at  which  meeting  said  rules  were  adopted  by  the 
unanimous  vote  of  all  present,  who  then  affixed  their  signatures  to  the  same,  since  which  others 
have  subscribed  their  names. 

Boston,  May  17,  1829. 

RULES. 

Section  1.  Ashlar  Stones  are  to  be  measured  on  their  fronts,  quoin-heads,  and  reveals 
against  doors,  windows,  and  recesses. 

Sect.  2.  Headers  or  binders,  that  make  the  thickness  of  the  wall,  are  to  be  measured  as  ash- 
lar-work, adding  their  beds,  or  builds. 

Sect.  3.  Double-headed  Quoins,  not  less  than  nine  inches  each  head,  are  to  be  measured  as 
ashlar-work,  adding  their  beds,  or  builds. 

Sect.  4.  Window-caps,  for  ashlar-work,  are  to  be  measured  on  their  fronts,  under  sides  that 
show,  and  reveals. 

Sect.  5.  Window-sills,  for  ashlar- work,  are  to  be  measured  on  their  tops  and  fronts,  the 
whole  thickness  of  their  rise,  and  half  their  under  sides. 

Sect.  6.  Belt  Stones,  for  ashlar  or  brick-work,  from  seven  to  nine  inches  rise,  and  the  usual 
thickness  of  ashlar-work,  are  to  be  cast  at  the  rate  of  a superficial  foot  to  each  foot  in  length. 

Sect.  7.  Arch  Stones,  in  ashlar- work,  are  to  be  measured  their  extreme  lengths  by  their  ex- 
treme widths,  adding  the  returns  and  reveals. 

Sect.  8.  Ashlar  Stones,  for  pediments  or  gable  ends  of  buildings,  and  other  similar  purposes, 
are  to  be  measured  their  extreme  lengths  by  their  extreme  widths. 

Sect.  9.  Plinths  are  to  be  measured  on  all  parts  that  show,  and  half  the  rough-hammered 
parts. 

Sect.  10.  Pilasters  are  to  be  measured  on  their  fronts,  returns,  and  reveals. 


RULES  FOR  MEASURING  HAMMERED  GRANITE. 


41 


Sect.  11.  Imposts  are  to  be  measured  on  their  fronts,  ends,  and  beds,  or  builds. 

Sect.  12.  Posts  or  Caps  are  to  be  measured  on  four  sides,  and  the  ends  of  caps  that  show. 

Sect.  13.  Posts  in  or  out  of  square  are  to  be  measured  on  four  sides,  squaring  from  their  ex- 
treme points. 

Sect.  14.  Door-sills,  under  posts,  are  to  be  measured  on  their  tops,  fronts,  and  ends,  and 
half  the  parts  hammered  under  the  ends. 

Sect.  15.  Window-sills,  between  posts,  are  to  be  measured  on  their  tops,  under  sides,  and 
their  whole  rise. 

Sect.  16.  Arch  Caps  and  Blocks,  that  make  the  thickness  of  the  wall,  are  to  be  measured  on 
four  sides,  the  extreme  lengths  by  their  extreme  widths. 

Sect.  17.  Belt  Stones,  that  make  the  thickness  of  the  wall,  are  to  be  measured  on  their 
fronts,  beds,  and  builds,  and  ends  that  show. 

Sect.  18.  Courses  of  Stones,  that  make  the  thickness  of  the  wall,  are  to  be  measured  on 
their  fronts,  beds,  and  builds. 

Sect.  19.  Door-steps  are  to  be  measured  on  their  tops,  fronts,  and  laps,  and  the  ends  that 
show,  which  ends  are  to  be  measured  at  the  rate  of  a superficial  foot  to  each  foot  on  the  width. 

Sect.  20.  Returns  for  steps,  from  six  to  ten  inches  rise,  are  to  be  measured  at  the  rate  of  a 
superficial  foot  to  each  foot  in  length. 

Sect.  21.  Platform  Stones  are  to  be  measured  as  steps;  when  two  or  more  are  required, 
half  the  edges  for  joints  are  to  be  added. 

Sect.  22.  Spiral  Steps  are  to  be  measured  their  e.xtreme  length  by  their  extreme  width,  rise, 
and  laps,  and  ends  that  show'. 

Sect.  23.  Fence  Stones  are  to  be  measured  on  their  fronts,  tops,  and  inside,  where  hammered, 
and  ends  that  show. 

Sect.  24.  Posts,  that  stand  in  the  ground,  are  to  be  measured  on  four  sides  and  tops,  and  half 
measurement  of  the  rough  parts  in  the  ground,  according  to  the  dimensions  of  the  hammered  parts. 

Sect.  25.  Cellar-door  Curbs  are  to  be  measured  on  their  tops  and  inside,  or  rise,  the  whole 
length  of  each  stone  ; the  rabbets  are  to  be  measured  the  length  of  each  stone  by  the  running  foot. 

Sect.  26.  Cellar-w'Indow  Curbs  are  furnished  by  the  piece. 

Sect.  27.  Well  Curbs  are  to  be  measured  on  the  outside  and  tops,  where  hammered  with 
the  jogs  and  corresponding  ends. 

Sect.  28.  Sesspool  Curbs  are  to  be  measured  as  Cellar-door  Curbs. 

Sect.  29.  Gutter  Stones  are  to  be  measured  on  the  top  side  by  the  superficial  foot ; Cutting 
Gutters  to  be  charged  extra. 

Sect.  30.  Edge  Stones  are  to  be  measured  by  the  running  foot,  double  measure  when  circular. 

Sect.  31.  Cutting  Scrools,  Jogs,  Rabbets,  Grooves,  Gutters,  and  Drilling  Holes  are 
extra  work,  and  do  not  add  to  or  diminish  from  the  measurement  of  the  work. 

Sect.  32.  Vault  Stones  are  to  be  measured  on  three  or  four  sides,  as  may  be  hammered,  and 
the  ends  that  show.  Floor  and  Ceiling  Stones,  more  than  nine  inches  in  thickness,  are  to  be  meas- 
ured on  one  side  and  two  edges,  and  the  ends  that  show  ; when  nine  inches  or  less  thickness,  on  one 
side  and  ends  that  show. 

Sect.  33.  All  Stones  not  included  in  the  foregoing  specifications,  on  account  of  their  irregular 
form  or  unfrequent  use,  should  be  measured  as  nearly  as  possible  according  to  the  rules  applying 
to  those  which  resemble  them. 

Sect.  34.  Those  which  differ  in  all  respects  must  be  furnished  by  the  piece. 

Sect.  35.  The  two  foregoing  observations  apply  to  Ornamental  Work,  the  parts  of  which  are 

6 


42 


PRACTICAL  MASONRY. 


so  minute,  and  generally  of  such  complicated  forms,  that  no  system  of  rules  sufficiently  short  and 
comprehensive  can  with  any  utility  be  adopted  ; with  regard,  however,  to  two  or  three  parts  of 
Ornamental  Work,  in  common  use,  it  may  be  well  to  state,  that  Cornice  is  usually  furnished  by 
the  running  foot ; Bases,  Columns,  and  Capitals,  by  the  piece. 

Sect.  36.  All  Circular  Work  to  be  charged  extra,  and  the  mode  of  measurement  should  be 
agreed  upon  at  the  time  said  work  is  contracted  for. 

William  Austin, 

Gridley  Bryant, 

Benjamin  Blaney, 

Jacob  Bacon, 

William  Crehore, 

Samuel  Currier, 

Levi  Cook, 

Conrad  C.  Carleton, 

James  C.  Ewer,  Jr., 

George  H.  Ewer, 

Joseph  Glass, 

Ephraim  Harrington, 

Thomas  Hollis, 

Charles  G.  Hall, 

Samuel  R.  Johnson, 

Nathaniel  Jewett, 

Sewall  Kendall, 


Allen  Litchfield,  Jr., 
Ward  Litchfield, 
Francis  Lawrence, 
James  McAllaster, 
Caleb  Metcalf, 
Samuel  Marden, 
Luther  Munn, 
Jonathan  Newcomb, 
Cushing  Nichols, 
Alexander  Parris, 
James  Page, 

William  Packard, 

Lot  Pool, 

Joseph  Richards, 

John  Redman, 

Wyatt  Richards, 


Alanson  Rice, 
Edward  Shaw, 
Zephaniah  Sampson, 
Franklin  Sawyer, 
Asa  Swallow, 

James  S.  Savage, 
Amos  C.  Sanborn, 

Job  Turner, 

Joseph  Tilden, 
Charles  Wells, 
William  Wood, 
Mordecai  L.  Wallis, 
Richard  Witherell, 
Henry  Wood, 
Jeremiah  Wetherbee, 
Salmon  Washburn. 


OF  CLAY 


43 


CHAPTER  II. 

SECTION  I.  — Clay. 

The  substances  included  under  this  term  are  mixtures  of  silex,  or  the  ingre- 
dient of  the  common  gun-flint  and  alumine  ; they  sometimes  contain  other  earths, 
or  metallic  oxyds,  by  the  latter  of  which  some  varieties  are  highly  colored. 
Their  hardness  is  never  great ; they  are  easily  cut  by  a knife,  may  in  general  be 
polished  by  friction  with  the  finger-nail,  and  are  usually  soft  to  the  touch.  When 
immersed  in  water  they  crumble  more  or  less  readily,  and  become  minutely 
divided.  Many  clays,  when  moistened,  yield  a peculiar  odor,  called  argillaceous  ; 
but  this  quality  appears  to  be  owing  to  the  presence  of  metallic  oxyds,  as  per- 
fectly pure  clays  do  not  possess  it. 

The  substances  which  are  properly  termed  clays  may,  by  a due  degree  of 
moisture  and  proper  management,  be  converted  into  a paste  more  or  less  tena- 
cious and  ductile,  which  constitutes  the  basis  of  several  kinds  of  pottery.  It 
possesses  a greater  or  less  degree  of  unctuosity,  and  is  capable  of  assuming 
various  forms  without  breaking.  This  argillaceous  paste,  when  dried,  becomes 
in  some  degree  hard  and  solid,  and,  by  exposure  to  a sufficient  degree  of  heat, 
may  be  made  to  assume  a stony  hardness. 

Clays  have  a strong  affinity  for  water;  hence  the  avidity  with  which  they 
imbibe  it ; hence,  also,  they  adhere  more  or  less  to  the  tongue  or  lips. 

Clay,  when  composed  of  only  silex  and  alumine,  in  any  proportions,  is  infusible 
in  a furnace,  and  even  when  somewhat  impure  it  resists  a degree  of  heat  without 
melting.  But  the  presence  of  other  earths,  particularly  of  lime,  or  of  a large 
quantity  of  oxyd  of  iron  with  a little  lime,  renders  it  fusible.  By  exposure  to 
heat  it  diminishes  in  bulk,  and  loses  somewhat  of  its  weight  by  the  escape  of 
water. 

Although  clay  is  essentially  composed  of  silex  and  alumine,  these  ingredients 
exist  in  various  proportions.  In  most  cases  silex  predominates,  being  in  the 
proportion  of  two,  three,  or  even  four  parts  to  one  of  alumine  ; sometimes  the  pro- 
portions are  nearly  equal,  and  in  some  cases  the  alumine  predominates.  The 
power  of  alumine  to  impress  its  character  on  the  compound,  although  present  in 
less  proportion  than  the  silex,  probably  arises  from  a greater  minuteness  of  its 
particles. 

The  color  of  clay  may  proceed  from  oxyd  of  iron,  or  from  some  bituminous  or 
vegetable  matter.  Hence  some  colored  clays,  when  exposed  to  heat,  become 


44 


PRACTICAL  MASONRY. 


white  by  the  destruction  of  their  combustible  ingredients,  while  others  suffer 
merely  a change  of  color,  by  the  action  of  oxygen  on  the  iron.  The  purer  clays 
are  white  or  gray,  and  suffer  little  or  no  change  by  the  action  of  fire. 

The  varieties  of  clay  are  numerous ; the  purest  kinds  are  extensively  used  in 
the  manufacture  of  porcelain  ware ; and  those  that  are  less  pure  are  burnt  into 
stone  ware  and  bricks. 

The  common  clays  may  be  divided,  in  regard  to  their  utility,  into  three  classes, 
the  Unctuous,  Meagre,  and  Calcareous. 

The  unctuous  contains,  in  general,  more  alumine  than  the  meagre,  and  the 
siliceous  ingredient  is  in  finer  grains  ; when  burnt  it  adheres  strongly  to  the 
tongue,  but  its  texture  is  not  visibly  porous.  When  containing  little  or  no  oxyd 
of  iron,  it  burns  to  a very  good  white  color,  and  is  very  infusible ; pipes  are  made 
of  it,  and  it  forms  the  basis  of  the  white  Staffordshire  ware.  If  it  contains  oxyd 
of  iron  sufficient  to  color  it  red,  when  baked,  it  becomes  much  more  fusible,  and 
can  only  be  employed  in  manufacturing  the  coarser  kinds  cf  pottery. 

Meagre  clay  is  such,  as,  when  dry,  does  not  take  a polish  from  rubbing  it  with 
the  nail ; it  feels  gritty  between  the  teeth,  and  the  sand  which  it  contains  is  in 
visible  grains.  When  burnt  without  addition,  it  has  a coarse  granular  texture, 
and  is  employed  in  the  manufacture  of  bricks  and  tiles. 

Calcareous  clay  effervesces  with  acids,  is  unctuous  to  the  touch,  and  always 
contains  iron  enough  to  give  it  a red  color  when  baked.  It  is  much  more  fusible 
than  any  of  the  preceding  kinds,  and  is  only  employed  in  brick-making.  By 
judicious  burning  it  may  be  made  to  assume  a semi- vitreous  texture,  and  bricks 
thus  made  are  very  durable. 

Clays  are  very  abundant  in  nature,  and  contribute  the  most  to  the  wants  and 
conveniences  of  man  of  all  the  earthy  minerals. 


SECTION  II.  — Brick-haking. 

The  clay  for  the  purpose  of  making  bricks  should  be  dug  in  the  autumn,  and 
piled  in  solid  heaps.  During  the  w'inter  it  should  be  broken  up,  and  exposed  in 
such  masses,  from  day  to  day,  as  to  become  thoroughly  penetrated  by  the  frost. 

In  the  spring  the  clay  is  to  be  broken  into  small  pieces,  and  shovelled  over,  in 
order  to  expel  the  frost.  After  this  is  done,  it  is  thrown  into  pits,  and  mixed  with 
fine  sand  and  a suitable  proportion  of  water ; the  sand  should  be  clear,  free  from 
lumps  of  marl  and  saline  particles,  — siliceous  sand  is  to  be  preferred,  — and  the 
water  must  be  fresh.  The  ingredients  are  to  be  worked  over  by  the  means  ot 


OF  BRICK-MAKING.  45 

the  shovel,  treacling,  or  the  wheel,  till  they  are  properly  incorporated,  and  are  of  a 
suitable  consistency.  In  this  way  they  are  prepared  for  the  striker’s  bench. 

In  preparing  for  a brick-yard,  the  surface  of  the  ground  should  be  cleared  and 
levelled ; a coat  of  sand,  two  or  three  inches  in  depth,  is  to  be  put  upon  it,  and 
rendered  as  hard  and  as  smooth  as  is  practicable,  by  passing  a heavy  roller  sev- 
eral times  over  it  when  wet.  After  this  a thin  layer  of  sand  is  sifted  upon  the 
surface,  and  a wooden  scraper  passed  over  it,  in  order  to  render  it  as  smooth  and 
even  as  possible.  The  yard  should  be  of  a size  sufficient  to  contain  the  bricks 
that  may  be  struck  in  two  days. 

Brick-moulds  are  commonly  made  to  contain  six  bricks  each.  The  striker  is 
prepared  with  two  moulds,  and  a trough  of  water.  When  the  prepared  clay  is 
shovelled  on  to  the  striker’s  table,  he  takes  his  mould  from  the  trough  of  water, 
adjusts  it  on  a thin,  level  board  bottom,  and  with  his  hands  wet,  to  prevent  adhe- 
sion, strikes  from  the  pile  of  mortar  or  prepared  clay  a quantity  a little  more  than 
sufficient  to  fill  one  of  the  apertures  of  the  mould,  which  he  drops  into  it  with 
considerable  force,  and  presses  it  firmly  down ; he  then  strikes  the  surplus  ofi’ 
with  his  hand,  and  thus  proceeds  (ill  all  the  apertures  of  the  mould  are  filled. 

A second  person  (called  the  carrier)  now  takes  the  full  mould  from  the  striker’s 
table  to  another  part  of  the  brick -yard,  and  puts  it  down  bottom  upwards.  The 
bottom  board  is  then  drawn  ofT  diagonally,  in  order  to  preserve  the  edges  of  the 
bricks  entire,  the  mould  is  raised,  and  the  bricks  left  on  the  sand  to  dry.  The 
carrier  returns  the  empty  mould  to  the  striker’s  trough,  takes  the  second  full 
mould,  and  deposits  the  bricks  as  before.  The  bricks  are  thus  exposed  in  ranges 
till  they  are  so  dry  as  not  to  be  easily  defaced ; they  are  then  placed  upon  their 
edges,  and  remain  till  they  are  dry  enough  to  be  put  into  hacks.  The  hacks  are 
composed  of  alternate  layers  of  bricks ; the  lirst  layer  is  called  stretcher,  and  the 
second  header ; interstices  or  spaces  are  left  between  the  bricks  of  from  three 
eighths  to  half  an  inch,  so  that  the  air  may  have  a free  circulation  between  them. 

The  bricks  ought  to  remain  in  this  situation  till  they  are  dry  enough  to  go  into 
the  kiln,  or  at  least  for  six  or  eight  weeks  of  dry  weather.  The  hacks  may  be 
of  the  thickness  of  three  or  four  bricks  placed  lengthwise,  and  six  or  eight  feet  hi 
height.  They  are  to  be  protected  from  storms  by  sheds  erected  for  the  pur- 
pose. 

In  forming  bricks  into  a kiln,  they  are  laid  in  benches,  with  arches,  or  apertures 
for  the  fuel.  A bench  is  formed  in  this  manner.  Courses  of  brick,  or  the 
stretchers,  are  laid  lengthwise ; and  across  the  stretchers,  or  at  right  angles  with 
them,  are  laid  other  courses,  or  headers  ; interstices  are  left  between  the  bricks 
from  one  fourth  to  one  half  an  inch  in  thickness.  The  stretchers  and  headers 
alternate  with  each  other,  and  four  courses  of  them  form  a bench.  Between 


46 


PRACTICAL  MASONRY. 


every  two  benches,  there  is  a space  left,  two  bricks’  length  in  breadth,  for  arches. 
The  arches  are  formed  by  the  gradual  projection  of  the  courses  in  the  two 
benches,  about  as  far  as  the  eighth  course,  where  the  courses  of  the  benches,  on 
each  side  of  the  space,  meet,  at  the  distance,  generally,  of  thirty-two  inches  from 
the  ground.  The  benches  are  commonly  raised  to  the  height  of  seven  or  eight 
feet.  Thus  the  benches  and  arches  alternate  with  each  other,  till  the  number  is 
increased,  as  it  may  be  deemed  expedient.  The  bricks  in  the  bench  are  placed 
on  their  edges,  and  care  should  be  taken  to  preserve  throughout  the  interstices 
between  their  sides  so  that  the  heat  may  percolate.  At  the  top  of  the  kiln,  the 
outside  walls  should  have  an  inclination  inwards,  of  about  one  foot  in  seven  of 
perpendicular  height.  The  kiln  is  faced  by  refuse  or  unburnt  bricks,  laid  up  in 
clay  mortar,  extending  round  the  whole  exterior  of  the  kiln,  the  thickness  of  the 
width  of  a single  brick.  The  mouths  of  the  arches  are  to  be  left  open,  and  flat 
stones  prepared  for  closing  them  w’hile  the  kiln  is  in  the  progress  of  burning. 

The  moulds  used  in  the  vicinity  of  Boston  are  commonly  eight  and  three 
eighths  inches  in  length,  two  and  one  eighth  in  thickness,  and  four  and  one 
half  in  width  ; and  bricks,  when  burnt,  vary  from  eight  to  seven  and  three 
fourths  inches  in  length,  and  are  about  four  inches  in  width,  and  two  in  thickness, 
according  to  the  length  of  time  and  the  degree  of  heat  to  which  they  have  been 
exposed. 

The  burning  is  commenced  with  a moderate  heat,  in  order  first  to  expel  the 
moisture.  When  this  is  done,  the  smoke  changes  from  a great  degree  of  black- 
ness to  a thin,  transparent  glimmering. 

Then  the  intensity  of  the  heat  is  increased  to  as  great  a degree  as  the  material 
will  bear,  without  being  fused,  which  is  continued  till  a contraction,  or  shrinkage, 
takes  place  at  the  top  of  the  kiln,  and  at  the  ends  of  the  arches  opposite  to  those 
in  which  the  fuel  is  placed.  When  this  is  the  case,  it  is  necessary  to  close  the 
mouths  of  the  arches  at  which  the  fuel  has  been  inserted,  and  to  put  it  in  at  the 
mouths  opposite.  At  the  close  of  the  process  of  burning,  the  arches  are  filled 
with  hard  wood  and  then  closed,  and  the  kiln  is  suflered  to  I’emain  thus  till  the 
bricks  are  sufficiently  cool  for  handling,  before  they  ai’e  exposed  to  the  air. 

A machine  has  recently  been  patented  and  put  in  operation  in  this  vicinity  for 
preparing  the  materials  for  brick,  which  seems  to  possess  many  advantages  over 
the  common  method.  The  machine  consists  of  a wheel  for  mixing  the  mortar, 
and  apparatus  for  filling  the  moulds,  and  is  worked  by  horse  or  steam  power. 
It  possesses,  among  others,  the  following  advantages : that  of  pulverizing  the  clay 
more  thoroughly,  and  producing  a more  homogeneous  and  compact  paste,  and  in 
consequence  the  bricks  are  less  liable  to  crack  in  the  operation  of  drying  or  burn- 
ing, and,  by  being  more  firmly  pressed  into  the  moulds,  the\’  are  less  liable  to 


OF  FACED  OR  PRESSED  BRICKS. 


47 


absorb  moisture  from  the  atmosphere,  and  are  rendered  smoother  ; and  as  less 
water  is  required  by  this  mode  in  making  the  paste,  the  bricks  do  not  require  the 
same  length  of  time  in  drying,  while  they  are  subject  to  shrink  less  in  burning 
than  in  the  common  method  ; and  lastly,  much  time  and  labor  are  saved  in  the 
operation. 


SECTION  III.  — Faced  or  Pressed  Bricks. 


These  bricks  are  used  to  form  the  facing  of  walls  in  the  better  kind  of  struc- 
tures,  and  are  finished  in  a machine.  The  roughness  and  change  of  form,  to 
which  common  bricks  are  liable,  is  owing  in  part  to  the  evaporation  of  a portion 
of  the  water  which  the  clay  contains.  To  remedy  the  difficulty  arising  from  this 
cause,  the  bricks,  after  being  moulded  in  the  common  manner,  are  exposed  to  the 
sun  till  they  are  nearly  di'ied,  retaining,  however,  sufiicient  plasticity  to  be  still 
capable  of  a slight  change  of  form.  The  moulds,  however,  are  somewhat  larger 
than  those  of  the  common  bricks,  in  oixler  that  the  bricks,  when  pressed,  may  be 
of  a sufficient  size.  The  press  machine  is  usuall}'  made  of  cast  iron,  and  contains 
a number  of  moulds  arranged  in  a circle  or  otherwise,  so  that  the  power  is  applied 
to  them  in  succession,  and  the  bricks  pressed  with  rapidity.  The  mould  is  of 
sufficient  thickness  to  resist  about  a ton’s  weight  applied  to  the  top  of  a follower. 
The  follower  is  fitted  as  near  as  practicable  to  the  inner  side  of  the  mould,  and 
kept  in  a proper  position  to  be  forced  through,  when  the  moulds  a'’e  removed 
from  their  beds.  This  is  done  by  the  means  of  a wheel  or  slide,  to  which  the 
mould  is  attached.  The  bricks,  being  pressed,  are  received  on  a carrying-board. 

The  force  is  applied  for  pressing  the  bricks  by  the  means  of  a double  pui'chase 
lever,  or  by  the  revolution  of  a wheel  wnth  rollers  running  on  an  oblique  plane. 

In  this  manner  about  five  thousand  bricks  may  be  pressed  olT  in  a day,  by  the 
labor  of  two  men  and  a horse. 

The  pressed  bricks  are  of  a superior  quality  in  point  of  durability  and  ele- 
gance. They  form  a w^all  with  a surface  of  great  smoothness,  and  when 
carefully  laid  produce  a pleasing  effect.  These  bricks  are  durable  from  their 
hardness  and  smoothness,  being  less  liable  to  decomposition  from  the  action  of 
the  atmosphere. 

A patent  was  obtained  in  England,  about  the  year  1795,  by  Mr.  Cartwright, 
for  an  improved  system  of  making  bricks,  of  which  the  following  extract  wall  fur- 
nish all  necessary  information. 

“Imagine  a common  brick,  w'ith  a groove  on  each  side  dowm  the  middle, 
rather  more  than  half  the  wddth  of  the  side  of  the  brick  ; a shoulder  will  thus  be 


48 


PRACTICAL  MASONRY. 


left  on  each  side  of  the  groove,  each  of  which  will  be  nearly  equal  to  one  quarter 
of  the  width  of  the  side  of  the  brick,  or  to  one  half  of  the  groove  or  rabbet.  A 
course  of  these  bricks  beifig  laid  shoulder  to  shoulder,  they  will  form  an  indented 
line  of  nearly  equal  divisions,  the  grooves  being  somewhat  wider  than  the  adjoin- 
ing shoulders,  to  allow  for  the  mortar  or  cement.  When  the  second  course  is 
laid  on,  the  shoulders  of  the  bricks  which  compose  it  will  fall  into  the  grooves  of 
the  first  course,  and  the  shoulders  of  the  first  course  will  fit  into  the  grooves  of 
the  second,  and  so  with  every  succeeding  course.  Buildings  constructed  of  these 
bricks  will  require  no  bond  timbers,  as  an  universal  bond  runs  through  the  whole 
building,  and  holds  all  the  parts  together;  the  walls  of  which  will  neither  crack 
nor  bilge  without  breaking  through  themselves.  When  bricks  of  this  construction 
are  used  for  arches,  the  sides  of  the  grooves  should  form  the  radii  of  a circle,  of 
which  the  intended  arch  is  a segment.  In  arch  work  the  bricks  may  either  be 
laid  in  mortar  or  dry,  and  the  interstices  afterwards  filled  up  by  pouring  in  lime, 
putty,  plaster  of  Paris,  &c.  Arches  of  this  kind,  having  any  lateral  pressure, 
can  neither  expand  -at  the  foot  or  spring  at  the  crown  ; consequently  they  need 
no  abutments;  neither  will  they  need  any  superincumbent  w’eight  on  the  crown 
to  prevent  them  from  springing  up.  The  centres  may  also  be  struck  immediately, 
so  that  the  same  centre,  which  never  need  be  many  feet  wide,  may  be  regularly 
shifted  as  the  work  proceeds.  But  the  most  striking  advantage  attending  this 
invention  is  the  security  it  affords  against  fire ; for,  from  the  peculiar  properties  of 
this  kind  of  arch,  requiring  no  abutments,  it  may  be  laid  upon  or  let  into  common 
walls,  no  stronger  than  what  are  required  for  timbers,  so  as  to  admit  of  brick 
floorings.” 


SECTION  IV.  — Brick  Masonry. 

The  use  of  bricks  in  building  may  be  traced  to  the  earliest  ages,  and  they  are 
found  among  the  ruins  of  almost  every  ancient  nation.  The  earliest  edifices  of 
Asia  were  constructed  of  bricks,  dried  in  the  sun  and  cemented  with  bitumen. 
Of  this  material  was  built  the  ancient  city  of  Nineveh.  The  walls  of  Babylon, 
some  of  the  ancient  structures  of  Egypt  and  Persia,  the  walls  of  Athens,  the 
rotunda  of  the  Pantheon,  the  Temple  of  Peace,  and  the  Thermae,  at  Rome,  were 
all  of  brick.  The  earliest  bricks  were  never  exposed  to  great  heat,  as  appears 
from  the  fact  that  they  contain  reeds  and  straw,  upon  which  no  mark  of  burning 
is  visible.  These  bricks  owe  their  preservation  to  the  extreme  dryness  of  the 
climate  in  which  they  remained,  since  the  earth  of  which  they  were  made  often 


OF  BRICK  MASONRY. 


49 


crumbles  to  pieces  when  immersed  in  water,  after  having  kept  its  shape  for  more 
than  two  thousand  years.  This  is  the  case  of  some  of  the  Babylonian  bricks, 
with  inscriptions  in  the  arrow-headed  character,  which  have  been  brought  to  this 
country.  The  ancients,  however,  at  a later  period,  burnt  their  bricks,  and  it  is 
these  chiefly  which  remain  at  the  present  day.  The  antique  bricks  were  larger 
than  those  employed  by  the  moderns,  and  were  almost  universally  of  a square 
form.  Those  of  Rome  appear  to  have  been  of  three  different  sizes ; the  largest 
were  about  twenty-two  inches  square,  and  two  and  one  fourth  inches  thick ; the 
second  size  sixteen  and  one  half  inches  square,  and  from  one  and  one  half  to 
two  inches  thick ; the  smallest  size  about  seven  and  one  half  inches  square,  and 
one  and  one  half  inches  thick.  In  order  to  secure  more  effectually  the  facing 
with  rubble,  the  Romans  placed  in  their  walls,  at  intervals  of  every  three  or  four 
feet,  two  or  three  courses  of  the  larger  brick.  (See  Plate  22,  Fig.  12.)  The 
larger  bricks  w'ere  used  in  the  formation  of  arches,  and  in  the  openings  of  build- 
ings. 

The  bricks  of  the  Greeks  were  commonly  cubical  and  of  different  sizes.  One 
size  was  a foot  on  all  sides,  another  kind  fifteen  inches;  the  former  w^as  chiefiy 
used  in  the  construction  of  private,  and  the  latter  in  public  edifices.  There  w^as 
a third  kind,  a foot  square  and  six  inches  thick,  and  a fourth  kind,  fifteen  inches 
square  and  seven  and  a half  inches  thick  ; these  last  two  kinds  were  called  half- 
bricks, and  were  used  for  the  purpose  of  better  effecting  the  construction  of  a 
bond.  (See  Plate  22,  Fig.  3.)  They  also  employed,  as  well  as  the  Romans, 
another  size,  for  ornamental  walls,  called  net- work.  (See  Plate  22,  Fig.  13.) 
This  net-work  had  a beautiful  appearance,  but  was  liable  to  crack ; in  conse- 
quence, according  to  Palladio,  there  are  no  ancient  specimens  of  this  kind 
remaining.  Vitruvius,  however,  states  the  form  of  these  bricks  to  have  been  a 
parallelogram,  six  inches  wide,  and  from  twelve  to  twenty-four  inches  long. 

The  baked  bricks  of  the  ancients  were  generally  made  of  two  parts  of  earth 
and  one  of  cinders,  well  tempered  together.  They  were  taken  from  the  moulds 
and  left  to  dry  in  the  sun  for  several  days,  and  afterwards  placed  in  a large  fur- 
nace, ranged  one  over  another,  at  some  distance  apart ; the  spaces  between  were 
filled  with  plaster,  or  a sort  of  strata  of  fine  coal. 

Besides  bricks  made  of  clay,  the  ancients  also  employed  a kind  of  factitious 
stone,  composed  of  a calcareous  mortar.  They  were  also  in  the  habit  of  using 
bricks  and  stones,  both  rubble  and  wrought,  in  the  same  wall. 

In  a rubble  wall,  three  courses  of  bricks  were  laid  at  intervals  of  two  or  three 
feet,  for  the  purpose  of  binding  the  mass  together ; the  angles  were  also  support- 
ed by  piers  of  stone  or  bricks.  (See  Plate  22,  Fig  11.) 

In  buildings  of  more  magnificence,  (see  Plate  22,  Fig.  12,)  the  rubble  was  con- 

7 


50 


PRACTICAL  MASONRY. 


cealed  in  the  wall.  The  bottom  of  the  wall  was  formed  of  six  courses  of  large 
bricks,  then  courses  of  smaller  bricks  were  laid  up  to  the  height  of  three  feet. 
Then  the  wall  was  bound  again  with  three  courses  of  large  bricks,  and  so  on. 
Examples  of  this  kind  of  wall  still  remain  in  the  Pantheon,  and  Warm  Baths 
of  Dioclesian. 


SECTION  V.  — Tiles. 

Tiles  are  plates  of  burnt  clay  resembling  bricks  in  their  composition  and  man- 
ufacture, and  used  for  the  covering  of  roofs.  They  are  necessarily  made  thicker 
than  slates,  or  shingles,  and  thus  impose  a greater  weight  upon  the  roofs.  Their 
tendency  to  absorb  water  promotes  the  decay  of  the  wood-work  beneath  them. 

Tiles  are  usually  shaped  in  such  a manner  that  the  edge  of  one  tile  receives 
the  edge  of  that  next  to  it,  so  that  water  cannot  percolate  between  them.  Tiles, 
both  of  burnt  clay  and  marble,  were  used  by  the  ancients,  and  the  former  con- 
tinue to  be  employed  in  various  parts  of  Europe.  Floors,  made  of  flat  tiles,  are 
used  in  many  countries,  particularly  in  France  and  Italy. 


SECTION  VI.  — Compact  Limestone. 

The  uses  and  geological  characters  of  this  substance  render  it  peculiarly 
interesting.  The  term  compact,  however,  as  applied  to  this  stone,  must  be 
received  with  some  latitude ; for,  although  its  texture  is  often  very  close  and  com- 
pact, sometimes  like  that  of  wax,  yet  in  other  instances  it  is  loose  and  earthy. 

Among  the  numerous  colors  of  compact  limestone,  the  most  frequent  are  the 
various  shades  of  gray,  such  as  smoke-gray,  yellowish-gray,  bluish-gray,  red- 
dish and  greenish-gray  ; it  is  also  seen  grayish-white,  grayish -black,  flesh-red, 
with  some  deep  tints  of  red  and  yellow ; several  of  these  colors  often  occur  in  the 
same  fragment,  which  are  distinguished  by  the  epithet  of  marbled. 

It  usually  occurs  in  extensive,  solid,  compact  masses,  whose  fracture  is  dull  and 
splintery,  or  even,  and  sometimes  conchoidal.  It  is  sometimes  traversed  by 
minute  veins  of  calcareous  spar,  which  reflect  a little  light ; and  some  compact 
limestones  are  also  slaty.  Its  hardness  is  somewhat  variable.  Its  specific  gravity 
usually  lies  between  2.40  and  2.75.  It  is  opaque  and  more  or  less  susceptible  of 
a polish. 

Compact  limestone  is  seldom,  perhaps  never,  a pure  carbonate  ; but  contains 
from  two  to  twelve  per  cent,  of  silex,  alumine,  and  the  oxyd  of  iron,  on  the  last 


OF  THE  BURNING  OF  LIME. 


51 


of  which  its  diversified  colors  depend.  In  fact,  by  increasing  the  proportion  of 
argillaceous  matter,  it  passes  into  marl.  Some  limestones,  which  effervesce  con- 
siderably with  an  acid,  are  still  so  impure,  that  they  melt  rather  than  bum  into 
lime. 

The  uses  to  which  compact  limestone  is  applied  are  various ; it  is  principally 
employed  as  a building  stone,  and  burnt  for  making  lime  and  mortar  ; nor  is  it  less 
important  to  the  agriculturist  as  a manure,  to  the  miner  as  a flux  for  the  reduc- 
tion of  ores,  to  the  soap-boiler,  to  the  tanner,  &c.  It  is  a substance  very  abun- 
dantly diffused  throughout  the  globe. 

It  is  from  compact  limestone,  that  lime,  so  extensively  used  in  the  arts,  is 
chiefly  obtained  ; pure  white  marble,  or  limestone,  undoubtedly  furnishes  the 
best  lime,  though  but  little  superior  to  that  obtained  from  gray,  compact  lime- 
stone. 

SECTION  VII. — The  Burning  of  Lime. 

This  is  a process  by  which  limestone,  marble,  shells,  &c.,  are  converted  into 
lime  by  means  of  heat,  in  kilns  properly  constructed  for  the  purpose.  By  the 
application  of  heat  to  any  of  these  substances,  their  carbonic  acid  is  driven  off, 
and  leaves  the  lime  in  a powder. 

The  calcination  of  limestone  may  be  effected  by  wood,  coal,  or  peat,  as  fuel ; but 
the  heat  should  not  much  exceed  a red  heat,  unless  the  stone  employed  he  nearly 
a pure  carbonate.  The  fuel  is  placed  in  layers,  alternately  with  those  of  the 
stones,  or  calcareous  materials  in  the  kilns,  and  the  process  of  burning  continued 
for  any  length  of  time,  by  repeated  applications  of  fuel  and  the  calcareous  mate- 
rials at  the  top ; the  lime  being  drawn  out  occasionally  from  below,  as  it  is  burnt. 

Fossil  or  mineral  coal  is  supposed  to  be  the  most  convenient  and  suitable 
material  for  effecting  this  business,  where  it  can  be  procured  plentifully,  and 
at  a sufficiently  cheap  rate;  as  it  bums  the  stone  or  other  calcareous  matter 
more  perfectly,  and  of  course  leaves  fewer  cores  in  the  calcined  pieces  than  when 
other  sorts  of  fuel  are  employed  for  the  purpose. 

Peat,  also,  is  highly  recommended,  for  its  cheapness  and  uniformity  of  heat. 
When  coal  is  used,  the  limestones  are  liable,  from  excessive  heat,  to  run  into  solid 
lumps,  which  may  be  avoided  by  the  use  of  peat,  as  it  keeps  them  in  an  open 
state,  and  admits  the  air  freely. 

Count  Rumford,  with  his  usual  attention  to  economy  in  fuel  and  in  the  ex- 
pense of  caloric,  has  invented  an  oven  for  preparing  lime.  It  has  the  form  of  a 
high  cylinder,  with  a hearth  at  the  side,  and  at  some  distance  above  the  base. 


52 


PRACTICAL  MASONRY. 


The  combustible  is  placed  on  the  hearth,  and  burns  with  an  inverted  or  reflected 
flame.  The  lime  is  taken  out  at  the  bottom,  while  fresh  additions  of  limestone 
are  made  at  the  top ; and  thus  the  oven  is  preserved  constantly  hot. 

Limestone  recently  dug,  and  of  course  moist,  calcines  more  easily  than  that 
which  has  become  dry  by  exposure  to  the  air ; in  the  latter  case  it  is  found  con- 
venient even  to  moisten  the  stone,  before  putting  it  into  the  kiln. 

Limestone  loses  about  four  ninths  of  its  weight  by  burning,  but  is  nearly  of  the 
same  bulk. 

Lime  thus  obtained  is  called  quicklime.  If  it  be  wet  with  water,  it  instantly 
swells  and  cracks,  becomes  exceedingly  hot,  and  at  length  falls  into  a white, 
soft,  impalpable  powder.  This  process  is  denominated  the  slacking  of  lime.  The 
compound  formed  is  called  the  hydrate  of  lime,  and  consists  of  about  three  parts 
of  lime  to  one  of  water.  When  intended  for  mortar,  it  should  immediately  be 
incorporated  with  sand,  and  used  without  delay,  before  it  imbibes  carbonic  acid 
anew  from  the  atmosphere.  Lime  doubles  its  bulk  by  slacking. 


SECTION  VIII.  — Of  Mortars  and  Cements. 

In  the  construction  of  works  in  masonry,  we  generally  employ  some  kind  of 
cementitious  matter  for  connecting  the  stones  together,  and  rendering  them  firm 
and  compact.  When  the  works  are  to  be  exposed  to  the  action  of  water  imme- 
diately after  being  built,  this  cementitious  matter  must  be  of  such  a nature  that 
it  will  harden  under  water.  Hence  it  is,  that  we  have  occasion  for  two  kinds  of 
mortar,  one  that  will  set  and  harden  under  water,  called  by  Smeaton  a water- 
mortar,  or  cement ; and  common  mortar  for  ordinary  buildings. 

Common  Mortar,  it  is  almost  superfluous  to  say,  is  a preparation  of  lime 
and  sand,  mixed  with  water,  which  serves  to  unite  the  stones  in  the  building  of 
walls,  &c.,  and  on  the  proper  or  improper  manner  in  which  such  mortar  is  pre- 
pared and  used  depends  the  durability  and  security  of  buildings ; we  shall,  there- 
fore, here  introduce  many  particulars  on  this  head,  discovered  by  Smeaton,  Dr. 
Higgins,  &c.,  but  which,  not  being  generally  known,  have  never  been  introduced 
into  general  practice. 

Limestone,  marble,  chalk,  or  shells,  may  be  used  to  burn  for  lime  for  common 
mortar,  all  these  substances  being  composed  chiefly  of  lime  and  carbonic  acid  ; 
and  if  a piece  of  one  of  them  be  slowly  burnt  or  calcined,  so  as  to  expel  the 
whole,  or  nearly  the  whole,  of  its  carbonic  acid,  it  loses  about  forty-four  per  cent, 
of  its  weight ; and  when  a small  quantity  of  water  is  added  to  the  calcined  mat- 
ter, it  swells,  gives  out  heat,  and  falls  into  a finely  divided  powder  called  slacked 
lime.  The  bulk  of  the  powder  is  about  double  that  of  the  limestone. 


OF  MORTAES  AND  CEMENTS. 


53 


If  this  powder  be  rapidly  formed  into  a stiff  paste  with  water,  it  sets  or  solidi- 
fies as  a hydrate  of  lime,  and  ultimately  hardens  by  the  absorption  of  carbonic 
acid  from  the  air.  This  constitutes  common  building  mortar.  Hydrate  of  lime 
consists  of  one  hundred  parts  of  lime  and  thirty-one  parts  of  water.  Common 
limestone  consists  of  carbonate  of  lime,  with  very  little  of  any  other  substances  ; 
it  produces  a white  lime,  which  slacks  freely  when  well  burnt ; it  dissolves  in 
diluted  muriatic  acid,  with  only  a small  portion  of  residue,  and  never  contains 
more  than  a trace  of  iron.  It  differs  much  in  external  characters,  as  chalk,  mar- 
ble, common  compact  limestone,  &c. 

These  limestones  do  not  form  cements  to  set  in  water,  without  the  addition  of 
other  kinds  of  cementing  matter  ; hence  they  are  usually  employed  only  for  com- 
mon mortar.  The  hardest  marble  and  the  softest  chalk  make  equally  good  lime 
when  well  burnt;  but  chalk-lime  will  slack  when  not  perfectly  burnt,  and,  there- 
fore, has  a sufficient  quantity  of  fire ; wdiereas  stone-lime  must  have  sufficient  to 
make  it  slack.  It  was  also  observed  by  Dr.  Higgins,  that  stone-lime  does  not  re- 
absorb carbonic  acid  so  rapidly  as  chalk-lime.  Lime  made  from  common  lime- 
stone sustains  very  little  injury  from  being  kept  after  it  has  been  formed  into 
mortar,  provided  the  air  be  effectually  excluded  ; indeed,  Alberti  mentions  an 
instance  of  some  which  had  been  covered  up  in  a ditch  for  a very  long  time,  and 
yet  was  found  to  be  of  an  excellent  quality. 

Sand.  To  employ  lime  alone  in  the  composition  of  mortar  would  render  it 
expensive  ; besides  it  would  be  of  inferior  quality.  The 'material  commonly  used 
to  mix  with  lime  is  sand,  and  this  sand  should  be  of  a hard  nature,  not  very  fine, 
but  angular,  and  having  considerable  affinity  for  lime ; also,  the  more  irregular  it 
is  in  size  the  better.  It  should  be  free  from  any  mixture  of  soft  or  earthy  mat- 
ter, if  it  can  be  procured  without.  The  reason  is  obvious  ; for  mortar  composed 
of  soft  sand  cannot  be  harder  than  that  sand.  Sea-sand  makes  good  mortar, 
particularly  water-mortar.  Very  hard  burnt  brick,  or  tile,  reduced  to  a coarse 
powder,  also  makes  an  excellent  substance  to  mix  with  lime,  for  many  purposes. 

The  best  proportion  of  sand  for  common  mortar  is  easily  ascertained  by  trial ; 
enough  should  be  added  to  render  the  mortar  rather  short  than  tough  under  the 
trowel.  The  proportion  varies  from  four  parts  of  sand  to  one  of  lime,  to  one  and 
one  fourth  parts  of  sand  to  one  of  lime,  by  measure  ; the  proportion  differing  ac- 
cording to  the  coarseness  of  the  sand,  the  nature  of  the  limestone,  and  the  pre- 
cautions used  in  burning  it ; all  set  proportions  being  universally  adhered  to  only 
by  those  who  are  utterly  ignorant  of  the  subject.  In  many  situations,  it  is  impos- 
sible to  procure  good  sand  except  at  an  enormous  expense. 

Making  Mortar.  The  instructions  given  by  Dr.  Higgins  for  making  stucco 
mortar  apply  only  when  a very  superior  kind  is  wanted  ; but  the  same  general 


54 


PRACTICAL  MASONRY. 


principles  ought  to  be  followed  even  with  the  commonest  kinds  of  mortar.  We 
will  therefore  insert  them  in  this  place. 

Of  sand,  the  following  kinds  are  to  be  preferred.  First,  drift-sand,  or  'pit-sand, 
which  consist  chiefly  of  hard,  quartzose,  flat-faced  grains,  with  sharp  angles.  Sec- 
ondly, that  which  is  the  freest,  or  may  be  most  easily  freed  by  washing,  from 
clay,  salts,  and  calcareous,  gypseous,  or  other  grains  less  hard  and  durable  than 
quartz.  Thirdly,  that  which  contains  the  smallest  quantity  of  pyrites,  or  heavy 
metallic  matter,  inseparable  by  washing.  And,  fourthly,  that  which  suffers  the 
smallest  diminution  of  its  bulk  by  washing.  Where  a coarse  and  fine  sand  of 
this  kind,  and  corresponding  in  the  size  of  their  grains  with  the  coarse  and  fine 
sands  hereafter  described,  cannot  be  easily  procured,  let  such  sand  of  the  fore- 
going quality  be  chosen,  as  may  be  sorted  and  cleansed  in  the  following  manner. 

Let  the  sand  be  sifted  in  streaming  cold  w'ater,  through  a sieve  which  shall 
give  passage  to  all  such  grains  as  do  not  exceed  one  sixteenth  of  an  inch  in  di- 
ameter ; and  let  the  stream  of  water  and  the  sifting  be  regulated  so  that  all  the 
sand  which  is  much  finer  than  the  Lynn  sand,  commonly  used  in  the  London 
glasshouses,  together  with  clay,  and  every  other  matter  specifically  lighter  than 
sand,  may  be  washed  away  with  the  stream  ; whilst  the  purer  and  coarser  sand, 
which  passes  through  the  sieve,  subsides  in  a convenient  receptacle,  and  the 
coarse  rubbish  and  rubble  remain  on  the  sieve,  to  be  rejected. 

Let  the  sand  which  thus  subsides  in  the  receptacle  be  washed  in  clean  stream- 
ing water,  through  a fine  sieve,  so  as  to  be  further  cleansed,  and  sorted  into  two 
parcels  ; a coarser,  which  will  remain  in  the  sieve,  which  is  to  give  passage  to 
such  grains  of  sand  only  as  are  less  than  one  thirtieth  of  an  inch  in  diameter,  and 
which  is  to  be  saved  apart,  under  the  name  of  coarse  sand;  and  a finer,  which 
will  pass  through  the  sieve  and  subside  in  the  water,  and  which  is  to  be  saved 
apart,  under  the  name  of  fine  sand.  Let  the  coarse  and  the  fine  sand  be  dried 
separately,  either  in  the  sun  or  on  a clean  plate,  set  on  a convenient  surface,  in 
the  manner  of  a sand  heat. 

Let  stone-lime  be  chosen  which  heats  the  most  in  slacking,  and  slacks  the 
quickest  when  duly  watered  ; that  which  is  the  freshest  made  and  closest  kept ; 
that  which  dissolves  in  distilled  vinegar  with  the  least  effervescence,  and  leaves 
the  smallest  residue  insoluble,  and  in  the  residue  the  smallest  quantity  of  clay, 
gypsum,  or  iron.  Let  the  lime  chosen  according  to  these  rules  be  put  in  a 
brass-wdred  sieve,  to  the  quantity  of  fourteen  pounds.  Let  the  sieve  be  finer 
than  either  of  the  foregoing ; the  finer  the  better  it  will  be.  Let  the  lime  be 
slacked,  by  plunging  it  into  a butt  filled  with  soft  water,  and  raising  it  out  quickly, 
and  suffering  it  to  heat  and  fume,  and,  by  repeating  this  plunging  and  raising 
alternately,  and  agitating  the  lime  until  it  be  made  to  pass  through  the  sieve  into 


OF  MORTARS  AND  CEMENTS. 


55 


the  water ; and  let  the  part  of  the  lime  which  does  not  easily  pass  through  the 
sieve  be  rejected ; and  let  fresh  portions  of  the  lime  be  thus  used,  until  as  many 
ounces  of  lime  have  passed  through  the  sieve  as  there  are  quarts  of  water  in  the 
butt. 

Let  the  water,  thus  impregnated,  stand  in  the  butt  closely  covered,  until  it  be- 
comes clear,  and  through  wooden  cocks,  placed  at  different  heights  in  the  butt, 
let  the  clear  liquor  be  drawn  off,  as  fast  and  as  low  as  the  lime  subsides,  for  use. 
This  clear  liquor  is  called  lime-water.  The  freer  the  water  is  from  saline  matter, 
the  better  will  be  the  cementing  liquor  made  with  it.  Let  fifty-six  pounds  of  the 
aforesaid  chosen  lime  be  slacked,  by  gradually  sprinkling  the  lime-water  on  it,  and 
especially  on  the  unslacked  pieces,  in  a close  clean  place.  Let  the  slacked  part 
be  immediately  sifted  through  the  last  mentioned  brass-wired  sieve ; and  let  the 
lime  which  passes  be  used  instantly,  or  kept  in  air-tight  vessels,  and  the  part  of 
the  lime  which  does  not  pass  through  the  sieve  be  rejected.  This  finer  and  rich- 
er part  of  the  lime,  which  passes  through  the  sieve,  may  be  called  purified  lime. 

Let  bone-ash  be  prepared  in  the  usual  manner,  by  grinding  the  whitest  burnt 
bones  ; but  let  it  be  sifted,  so  as  to  be  much  finer  than  the  bone-ash  commonly 
sold  for  making  cupels. 

The  best  materials  for  making  cement  being  thus  prepared,  take  fifty-six 
pounds  of  the  coarse  sand,  and  forty- two  pounds  of  white  sand  ; mix  them  on  a 
large  plank  of  hard  wood,  placed  horizontally  ; then  spread  the  sand  so  that  it 
may  stand  to  the  height  of  six  inches,  with  a flat  surface  on  the  plank  ; wet  it 
with  the  lime-water,  and  let  any  superfluous  quantity  of  the  liquor,  which  the  sand 
in  the  condition  described  cannot  retain,  flow  away  off  the  plank.  To  the  wetted 
sand  add  fourteen  pounds  of  the  purified  lime,  in  several  successive  portions, 
mixing  and  beating  them  up  together,  in  the  mean  time,  with  the  instruments 
generally  used  in  making  fine  mortar  ; then  add  fourteen  pounds  of  the  bone-ash, 
in  successive  portions,  mixing  and  beating  all  together. 

The  quicker  and  the  more  perfectly  these  materials  are  mixed  and  beaten  to- 
gether, and  the  sooner  the  cement  thus  formed  is  used,  the  better  it  will  be. 
This  may  be  called  coarse-grained  cement,  which  is  to  be  applied  in  building, 
pointing,  plastering,  stuccoing,  or  other  work,  as  mortar  and  stucco  generally  are ; 
with  this  difference  chiefly,  that,  as  this  cement  is  shorter  than  mortar,  or  common 
stucco,  and  dries  sooner,  it  ought  to  be  worked  expeditiously,  in  all  cases ; and 
in  stuccoing  it  ought  to  be  laid  on  by  sliding  the  trowel  upwards  on  it.  The 
materials  used  along  with  this  cement,  in  building,  or  the  place  on  which  it  is  to 
be  laid,  in  stuccoing,  ought  to  be  well  wetted  with  the  lime-water,  in  the  instant 
of  laying  on  the  cement.  The  lime-water  is  also  to  be  used  when  it  is  necessary 
to  moisten  the  cement,  or  when  a liquid  is  required  to  facilitate  the  floating  of  the 
cement. 


56 


PRACTICAL  MASONRY. 


When  such  cement  is  required  to  be  of  a still  finer  texture,  take  ninety-eight 
pounds  of  the  fine  sand,  wet  it  with  the  lime-water,  and  mix  it  with  the  purified 
lime  and  the  bone-ash,  in  the  quantities  and  in  the  manner  described  ; with  this 
difference  only,  that  fifteen  pounds  of  lime,  or  thereabouts,  are  to  be  used  instead 
of  fourteen  pounds,  if  the  greater  part  of  the  sand  be  as  fine  as  Lynn  sand. 
This  may  be  called  fine-grained  cement.  It  is  used  in  giving  the  last  coating,  or 
the  finish,  to  any  work  intended  to  imitate  the  finer-grained  stones,  or  stucco. 
But  it  may  be  applied  to  all  uses  of  the  coarse-grained  cement,  and  in  the  same 
manner. 

When,  for  any  of  the  foregoing  purposes  of  pointing,  building,  &c.,  a cement 
is  required  much  cheaper  and  coarser-grained  than  either  of  the  foregoing,  then 
much  coarser  clean  sand  than  the  foregoing  coarse  sand,  or  well  washed  fine 
rubble,  is  to  be  provided.  Of  this  coarse  sand,  or  rubble,  take  fifty-six  pounds ; 
and  after  mixing  these,  and  wetting  them  with  the  cementing  liquor,  in  the  fore- 
going manner,  add  fourteen  pounds,  or  somewhat  less,  of  the  purified  lime,  and 
then  fourteen  pounds,  or  somewhat  less,  of  the  bone-ash,  mixing  together  in  the 
manner  already  described.  When  the  cement  is  required  to  be  white,  white  sand, 
white  lime,  and  the  whitest  bone-ash  are  to  be  chosen.  Gray  sand,  and  gray 
bone-ash,  formed  of  half-burnt  bones,  are  to  be  chosen  to  make  cement  gray  ; 
and  any  other  color  of  the  cement  is  obtained,  either  by  choosing  colored  sand, 
or  by  the  admixture  of  the  necessary  quantity  of  colored  talc,  in  powder,  or  of 
colored,  vitreous,  or  metallic  powders,  or  other  durable  coloring  ingredients  com- 
monly used  in  paint. 

This  cement,  whether  the  coarse  or  fine-grained,  is  applicable  in  forming  arti- 
ficial stone,  by  making  alternate  layers  of  the  cement  and  of  flint,  hard  stone,  or 
bricks,  in  moulds  of  the  intended  stone,  and  by  exposing  the  masses  so  formed 
to  the  open  air,  to  harden. 

When  such  is  required  for  water-fences,  two  thirds  of  the  prescribed  quantity 
of  bone-ashes  are  to  be  omitted  ; and,  in  the  place  thereof,  an  equal  measure  of 
powdered  terras  is  to  be  used  ; and  if  the  sand  employed  be  not  of  the  coarsest 
sort,  more  terras  must  be  added,  so  that  the  terras  shall  be  one  sixth  part  of  the 
weight  of  the  sand. 

When  such  a cement  is  required  of  the  finest  grain,  or  in  a fluid  form,  so  that 
it  may  be  applied  with  a brush,  flint-powder,  or  the  powder  of  any  quartzose  or 
hard  earthy  substance,  may  be  used  in  the  place  of  sand,  but  in  a quantity  smaller 
in  proportion  as  the  flint  or  other  powder  is  finer ; so  that  the  flint-powder,  or 
other  such  powder,  shall  not  be  more  than  six  times  the  weight  of  the  lime,  nor 
less  than  four  times  its  weight.  The  greater  the  quantity  of  lime  within  these 
limits,  the  more  will  the  cement  be  liable  to  crack  by  quick  drymg,  and  vice  versa. 


OF  MORTARS  AND  CEMENTS. 


57 


Where  the  above-described  sand  cannot  be  conveniently  procured,  or  where 
the  sand  cannot  be  conveniently  washed  and  sorted,  that  which  most  resembles 
the  mixture  of  coarse  and  fine  sand  above  prescribed  may  be  used,  as  directed, 
provided  due  attention  be  paid  to  the  quantity  of  the  lime,  w^hich  is  to  be  greater 
as  the  quality  is  finer,  and  vice  versa. 

Where  sand  cannot  be  easily  procured,  any  durable  stony  body,  or  baked 
earth,  grossly  powdered  and  sorted  nearly  to  the  sizes  above  prescribed  for 
sand,  may  be  used  in  the  place  of  sand,  measure  for  measure,  but  not  weight  for 
weight,  unless  such  gross  powder  be  specifically  as  heavy  as  sand. 

Sand  may  be  cleansed  from  every  softer,  lighter,  and  less  durable  matter,  and 
from  that  part  of  the  sand  which  is  too  fine,  by  various  methods,  preferable,  in 
certain  circumstances,  to  that  which  has  been  already  described. 

Water  may  be  found  naturally  free  from  fixable  gas,  selenite,  or  clay ; such 
^vater  may,  without  any  great  inconvenience,  be  used  in  the  place  of  the  lime- 
w'ater ; and  water  approaching  this  state  will  not  require  so  much  lime  as  above 
prescribed  to  make  the  lime-water ; and  a lime-w’ater  sufficiently  useful  may  be 
made  by  various  methods  of  mixing  lime  and  water,  in  the  described  proportions, 
or  nearly  so. 

When  stone-lime  cannot  be  procured,  chalk-lime,  or  shell-lime,  which  best  re- 
sembles stone-lime  in  the  foregoing  characters  of  lime,  may  be  used  in  the  man- 
ner described,  excepting  that  fourteen  pounds  and  a half  of  chalk -lime  will  be 
required  in  the  place  of  fourteen  pounds  of  stone-lime.  The  proportion  of  lime, 
as  prescribed  above,  may  be  increased  without  inconvenience,  when  the  cement 
or  stucco  is  to  be  applied  where  it  is  not  liable  to  dry  quickly ; and,  in  the  con- 
trary case,  this  proportion  may  be  diminished.  The  defect  of  lime,  in  quantity  or 
quality,  may  be  very  advantageously  supplied  by  causing  a considerable  quantity 
of  lime-water  to  soak  into  the  work,  in  successive  portions,  and  at  distant  intervals 
of  time  ; so  that  the  calcareous  matter  of  the  lime-water,  and  the  matter  attracted 
from  the  open  air,  may  fill  and  strengthen  the  work. 

The  powder  of  almost  every  well  dried  or  burnt  animal  substance  may  be  used 
instead  of  bone-ash ; and  several  earthy  powders,  especially  the  micaceous  and 
the  metallic ; and  the  elixated  ashes  of  divers  vegetables,  whose  earth  will  not 
burn  to  lime,  as  well  as  the  ashes  of  mineral  fuel,  which  are  of  the  calcareous 
kind,  but  will  not  burn  to  lime,  will  answer  the  ends  of  bone-ash,  in  some  degree. 
The  quantity  of  bone-ash  described  may  be  lessened  without  injuring  the  ce- 
ment ; in  those  circumstances,  especially,  which  admit  the  quantity  of  lime  to  be 
lessened,  and  in  those  wherein  the  cement  is  not  liable  to  dry  quickly.  The  art 
of  remedying  the  defects  of  lime  may  be  advantageously  practised  to  supply  the 
deficiency  of  bone-ash,  especially  in  building  and  making  artificial  stone  with  this 
cement. 


8 


58 


PRACTICAL  MASONRY. 


As  the  preceding  method  of  making  mortar  differs,  in  many  particulars,  from 
the  common  process,  it  may  be  useful  to  inquire  into  the  causes  on  which  this 
difference  is  founded. 

When  the  sand  contains  much  clay,  the  workmen  find  that  the  best  mortar 
they  can  make  must  contain  about  one  half  lime ; and  hence  they  lay  it  down  as 
certain,  that  the  best  mortar  is  made  by  the  composition  of  half  sand  and  half 
lime. 

But  with  sand  requiring  so  great  a proportion  of  lime  as  this,  it  will  be  impos- 
sible to  make  good  cement ; for  it  is  universally  allowed  that  the  hardness  of 
mortar  depends  on  the  crystallization  of  the  lime  round  the  other  materials  which 
are  mixed  with  it,  and  thus  uniting  the  whole  mass  into  one  solid  substance. 
But  if  a portion  of  the  materials  used  be  clay,  or  any  other  friable  substance,  it 
must  be  evident,  that,  as  these  friable  substances  are  not  changed  in  one  single 
particular  by  the  process  of  being  mixed  up  with  lime  and  water,  the  mortar  of 
which  they  form  a proportion  will  consequently  be  more  or  less  of  a friable  nature, 
in  proportion  to  the  quantity  of  friable  substances  used  in  the  composition  of  the 
mortar.  On  the  other  hand,  if  mortar  be  composed  of  lime  and  good  sand  only, 
as  the  sand  is  a stony  substance,  and  not  in  the  least  friable,  and  as  the  lime,  by 
perfect  crystallization,  becomes  likewise  of  a stony  nature,  it  must  follow,  that  a 
mass  of  mortar,  composed  of  these  two  stony  substances,  will  itself  be  a hard, 
solid,  unfriable  substance.  This  may  account  for  one  of  the  essential  variations 
in  the  preceding  method  from  that  in  common  use,  and  point  out  the  necessity 
of  never  using  in  the  place  of  sand,  which  is  a durable,  stony  body,  the  scrap- 
ings of  roads,  old  mortar,  and  other  rubbish  from  ancient  buildings,  which  are 
frequently  made  use  of,  as  all  of  them  consist,  more  or  less,  of  muddy,  soft,  and 
minutely  divided  particles.  Another  essential  point  is  the  nature  and  quality  of 
lime.  Now  experience  proves,  that,  when  lime  has  been  long  kept  in  heaps  or 
untight  casks,  it  is  reduced  to  the  state  of  chalk,  and  becomes  every  day  less 
capable  of  being  made  into  good  mortar ; because,  as  the  goodness  or  durability 
of  the  mortar  depends  on  the  crystallization  of  the  lime,  and  as  experiments  have 
proved  that  lime,  when  reduced  to  this  chalk -like  state,  is  always  incapable  of 
perfect  crystallization,  it  must  follow  that,  as  lime  in  this  state  never  becomes 
crystallized,  the  mortar,  of  which  it  forms  the  most  indispensable  part,  will  neces- 
sarily be  very  imperfect ; that  is  to  say,  it  will  never  become  a solid  stony  sub- 
stance ; a circumstance  absolutely  required  in  the  formation  of  good  durable 
mortar.  These  are  the  two  principal  ingredients  in  the  formation  of  mortar ; but, 
as  water  is  also  necessary,  it  may  be  useful  to  point  out  which  is  the  fittest  for 
this  purpose ; the  best  is  rain-water,  river-water  the  second,  land-water  next, 
and  spring-water  last.  The  ruins  of  the  ancient  Roman  buildings  are  found  to 


OF  MORTAES  AND  CEMENTS. 


59 


cohere  so  strongly,  as  to  have  caused  an  opinion  that  their  constructors  were 
acquainted  with  some  kind  of  mortar  which,  in  comparison  with  ours,  might  just 
ly  be  called  cement;  and  that  to  our  ignorance  of  the  materials  they  used  is 
owing  the  great  inferiority  of  modern  buildings  in  their  durability.  But  a proper 
attention  to  the  above  particulars  would  soon  show,  that  the  durability  of  the 
ancient  edifices  depended  on  the  manner  of  preparing  their  mortar  more  than  on 
the  nature  of  the  materials  used.  The  following  observation  will,  we  think, 
prove  this  beyond  a possibility  of  doubt.  Lime  which  has  been  slacked  and 
mixed  with  sand  becomes  hard  and  consistent  when  dry,  by  a process  similar  to 
that  which  produces  stalactites  in  caverns.  These  are  always  formed  by  water 
dropping  from  the  roof.  But  when  the  small  drop  of  water  comes  to  be  exposed 
to  the  air,  the  calcareous  matter  contained  in  it  begins  to  separate  from  the  water, 
and  to  reassume  its  native  form  of  limestone  or  marble. 

When  the  calcareous  matter  is  perfectly  crystallized  in  this  manner,  it  is,  to  all 
intents  and  purposes,  limestone  or  marble  of  the  same  consistence  as  before.  If 
lime  in  a caustic  state  be  mixed  with  water,  part  of  the  lime  will  be  dissolved, 
and  will  also  begin  to  crystallize.  The  water  which  parted  with  the  crystallized 
lime  will  then  begin  to  act  upon  the  remainder,  which  it  could  not  dissolve 
before,  and  thus  the  process  will  continue,  either  till  the  lime  be  all  reduced  to 
an  effete  or  crystalline  state,  or  something  hinders  the  action  pf  water  upon  it.  It 
is  this  crystallization  which  is  observed  by  the  workmen  when  a heap  of  lime  is 
mixed  with  water,  and  left  for  some  time  to  macerate.  A hard  crust  is  formed 
upon  the  surface,  which  is  ignorantly  called  frostling,  though  it  takes  place  in 
summer  as  well  as  in  winter. 

If,  therefore,  the  hardness  of  the  lime,  or  its  becoming  a cement,  depends  en- 
tirely on  the  formation  of  its  crystals,  it  is  evident  that  the  perfection  of  the  cement 
must  depend  on  the  perfection  of  the  crystals,  and  the  hardness  of  the  matters 
which  are  entangled  among  them.  The  additional  substances  used  in  making  of 
mortar,  such  as  sand,  brick-dust,  or  the  like,  serve  only  for  a purpose  similar  to 
what  is  answered  by  sticks  put  into  a vessel  full  of  any  saline  solution  : namely, 
to  afford  the  crystals  an  opportunity  of  fastening  themselves  upon  it.  If,  therefore, 
the  matter  interposed  between  the  crystals  of  the  lime  is  of  a friable,  brittle  na- 
ture, such  as  brick-dust  or  chalk,  the  mortar  will  be  of  a weak  and  imperfect  kind; 
but  when  the  particles  are  hard,  angular,  and  very  difficult  to  be  broken,  such  as 
those  of  river  or  pit-sand,  the  mortar  turns  out  exceedingly  good  and  strong. 

That  the  crystallization  may  be  the  more  perfect,  a large  quantity  of  water 
should  be  used,  the  ingredients  be  perfectly  mixed  together,  and  the  drying  be 
as  slow  as  possible.  An  attention  to  these  particulars,  and  to  the  quality  of  bricks 
and  stones,  would  make  the  buildings  of  the  moderns  equally  durable  with  those 


60 


PRACTICAL  MASONRY. 


of  the  ancients.  In  the  old  Roman  works,  the  great  thickness  of  the  walls  neces- 
sarily required  a vast  time  to  dry.  The  middle  of  them  was  composed  of  peb- 
bles, thrown  in  at  random,  and  which  evidently  had  thin  mortar  poured  in  among 
them.  Thus  a great  quantity  of  the  lime  would  be  dissolved,  and  the  crystalli- 
zation performed  in  the  most  perfect  manner.  The  indefatigable  pains  and  per- 
severance, for  which  the  Romans  were  so  remarkable  in  all  their  undertakings, 
leave  no  room  to  doubt  that  they  w’ould  take  care  to  have  the  ingredients  mixed 
together  as  well  as  possible.  The  consequence  of  all  this  is,  that  the  buildings 
formed  in  this  manner  are  all  as  firm  as  if  cut  out  of  a solid  rock,  the  mortar 
being  equally  hard,  if  not  more  so  than  the  stones  themselves. 

Water  Mortars  or  Cements.  The  cementing  materials  are  either  found 
ready  combined  in  certain  kinds  of  stone,  as  in  the  case  of  Roman  cement ; or 
the  effect  is  produced  by  mixture,  as  when  we  mix  the  lime  of  poor  limestones 
with  Dutch  terras.  The  natural  combination  is,  however,  by  far  the  best,  and 
it  is  only  in  cases  where  the  other  can  be  obtained  at  a much  less  expense,  that 
we  advise  it  to  be  resorted  to ; but  for  such  cases  we  propose  to  describe  the 
best  compositions  now  known. 

Roman  Cement  is  made  from  the  kind  of  stones  called  clay-balls.  The  best 
stone  contains  about  sixty  per  cent,  of  carbonate  of  lime,  and  eight  or  ten  per  cent, 
of  protoxyd  of  iron,  the  rest  being  silex  and  alumine,  nearly  in  equal  parts.  The 
inferior  stones  contain  peroxyd  of  iron,  and  often  soluble  earthy  and  alkaline  salts. 
Stone  of  the  best  kind  is  produced  on  the  coast  of  the  Isle  of  Sheppy,  and  from 
the  alum-shale  on  the  coast  of  Yorkshire,  near  Whitby.  Stone  of  an  inferior 
quality  is  procured  near  Harwich,  and  other  places  on  the  coast  of  England,  and 
at  Boulogne,  in  France.  The  stone  is,  after  being  broken  to  a proper  size,  slow- 
ly calcined  in  kilns  or  ovens,  and  then  it  is  ground  to  a fine  powder,  of  a light 
snuff  color,  when  the  stone  is  good,  and  of  a deeper,  approaching  to  a burnt  um- 
ber-brown, when  the  quality  is  inferior.  The  powder  should  be  kept  perfectly 
dry,  till  it  is  used  ; and,  in  order  to  use  it,  mix  it  with  not  less  than  an  equal  por- 
tion, by  measure,  of  dry,  clean,  and  sharp  river-sand ; then  add  as  much  clear 
water  as  will  form  it  into  a stiff  paste,  but  not  more  ; and  the  whole  that  is  so 
mixed  must  be  used  before  it  begins  to  set,  which,  with  good  cement,  happens 
in  about  fifteen  minutes  from  the  time  of  adding  water ; but,  in  cements  very  fit 
for  building,  the  setting  may  not  be  commenced  in  less  than  half  or  three  quarters 
of  an  hour.  When  the  setting  begins,  all  the  moisture  on  the  surface  disappears, 
and  the  cen>ent  feels  dry  and  warm  to  the  touch,  and  hardens ; the  hardening 
continues  for  some  months,  and  is  increased  by  frequently  wetting  the  work,  in 
cases  where  it  has  not  to  be  exposed  to  water  immediately  on  its  being  set.  A 
coat  of  this  cement  is  impervious  to  water,  and  it  is  therefore  used  for  lining  cis- 


OF  MORTARS  AND  CEMENTS. 


61 


terns,  tanks,  reservoirs,  &c.  Roman  cement  may  be  used  alone,  but  it  does  not 
become  so  hard  and  durable  as  when  it  has  a proper  quantity  of  good  sand 
mixed  with  it.  A mixture  of  Roman  cement  and  common  mortar  should  never 
be  made,  for  their  setting  properties  depend  on  different  combinations,  which 
interfere  with  each  other  when  acting  in  the  same  mass  ; and  the  best  mortar  and 
best  cement  may  be  both  rendered  worthless  by  mixture.  In  using  cement 
the  more  expeditious  the  workman  is  in  his  operations  the  better ; and  when 
once  setting  has  commenced,  the  work  should  be  no  further  disturbed.  If  the 
setting  take  place  too  rapidly  for  the  nature  of  the  work,  let  the  cement,  in  pow- 
der, be  spread  out  so  as  to  expose  a large  surface  to  the  air,  in  a dry  place  ; in 
this  manner  the  time  of  setting  may  be  extended  according  to  the  time  the  pow- 
der is  exposed  ; and  though  the  quality  of  the  cement  is  injured  by  the  process, 
it  is  not  so  much  destroyed  as  by  working  the  cement  after  its  being  partially  set. 

Puzzolana  Mortar.  An  excellent  mortar  for  water- works  is  formed  b}^  com- 
bining the  lime  of  poor  limestones  with  the  earth  called  puzzolana,  which  is 
procured  in  Italy.  The  limestones  adapted  for  this  purpose  are  the  blue  lias  of 
Somersetshire,  the  clunch  of  Sussex,  and  the  hard,  gray  chalk  of  Surrey.  Smea- 
ton  used  the  lime  of  the  lias,  procured  at  Aberthaw,  in  Wales,  for  the  Eddystone 


lighthouse,  the  proportions  as 

follows : — 

Kind  o f Mortar, 

Lime  in  Powder. 

Puzzolana. 

Cleati  Sand. 

No.  1.  Eddystone  Mortar, 

2 bushels. 

2 bushels. 

No.  2.  Stone  Mortar, 

2 “ 

1 

1 bushel. 

No.  3.  Do.  (2d  sort). 

2 “ 

1 “ 

2 “ 

No.  4.  Face  Mortar, 

2 “ 

1 

3 “ 

No.  5.  Do.  (2d  sort). 

2 “ 

4 “ 

3 “ 

No.  6.  Backing  Mortar, 

2 “ 

i “ 

3 “ 

Smeaton  remarks,  that  mortar  of  the  proportions  of  No.  1 will,  in  twelve  months, 
acquire  the  hardness  of  Portland  stone,  when  under  water ; and  the  others  will 
in  time  acquire  a stony  hardness,  if  the  materials  have  been  thoroughly  mixed  and 
well  beaten  together.  An  article  called  British  puzzolana  has  lately  been  manu- 
factured, but  it  does  not  possess  the  same  properties  as  the  foreign  kind,  and,  in- 
deed, is  rather  a substitute  for  sand  than  for  the  true  puzzolana. 

Terras  Mortar  is  also  very  good  for  water-works  ; it  is  composed  of  an 
earthy  material  called  terras,  found  near  Andernach,  in  the  department  of  the 
Rhine  and  Moselle,  which  is  mixed  with  any  lime  of  a nature  similar  to  the  blue 
lias.  Terras  is  much  used  by  the  Dutch,  for  their  sea  and  canal  works,  and  it 
has  the  singular  property  of  forming  stalactitical  excrescences  at  the  joints  of  the 
work.  Smeaton  employed  it  in  the  following  proportions,  according  to  the  nature 
of  the  work.  No.  1 being  the  best  quality. 


62 


PRACTICAL  MASONRY. 


No.  1.  Terras  Mortar, 


Kind  of  Mortar. 


Lime  in  Powder. 
2 bushels, 


Terras. 

1 bushel. 


Clean  Sand. 


No.  2.  Do.  (2d  kind). 

No.  3.  Do.  (3d  kind). 

No.  4.  Do.  (4lh  kind). 

No.  5.  Backing  Mortar, 


2 “ 
2 “ 
2 “ 
2 “ 


1 “ 
2 


1 “ 
1 “ 
1 “ 


2 “ 
3 “ 

3 “ 


1 bushel. 


The  customary  allowance  of  beating  for  terras  mortar  is  a day’s  work  of  a man 
for  every  bushel  of  terras.  When  neither  Roman  cement,  puzzolana,  nor  terras 
can  be  procured,  except  at  great  expense,  then  we  may  have  recourse  to  cal- 
cined iron  ore,  scales  from  smiths’  forges,  calcined  basalt,  clay,  and  other  sub- 
stances containing  a considerable  proportion  of  protoxyd  of  iron.  Lime  may 
also  be  improved  by  peculiar  treatment  in  burning,  for  it  appears  that  even  com- 
mon chalk-lime  acquires  a setting  property  resembling  that  of  the  lias-lime,  by 
being  long  exposed  to  a certain  degree  of  heat.  All  limes  fit  for  water-cements 
require  to  be  ground  to  powder,  and  the  finer  the  better.  If  these  limes  be 
slacked,  the  setting  property  is  partially  destroyed  ; and  it  is  important  that  no 
more  mortar  should  be  made  up  at  once  than  can  be  used  within  a few  hours. 


These  are  the  substances  generally  made  use  of  for  the  uniting  medium  be- 
tween bricks  or  stones,  in  forming  them  into  buildings.  Though  many  experi- 
ments have  been  made  to  ascertain  the  best  materials  for  these  compounds,  and 
the  mode  of  mixing  them,  and  not  without  a degree  of  success,  still  much  yet 
seems  to  remain  to  be  discovered.  A composition  of  lime,  sand,  and  water,  in 
consequence  of  the  facility  with  which  they  pass  from  a soft  state  to  a stony  hard- 
ness, has,  in  common  uses,  superseded  all  other  ingredients.  But  in  order  that 
the  mortar  should  be  of  a good  quality,  great  care  and  skill  are  requisite  in  the 
selection  of  the  materials  and  the  proportioning  of  them  ; and  much  depends  on 
the  degree  of  labor  bestowed  on  the  mixing  and  incorporation.  The  lime  should 
be  well  burnt,  and  free  from  fixed  air  and  carbonic  acid.  Hence,  lime  that  has 
become  effete,  from  exposure  to  the  atmosphere,  is  impaired  in  its  quality.  The 
sand  most  proper  for  mortar  is  that  which  is  wholly  siliceous,  and  which  is  sharp, 
that  is,  not  having  its  particles  rounded  by  attrition.  Fresh  sand  is  to  be  pre- 
ferred to  that  taken  from  the  vicinity  of  the  sea-shore,  the  salt  of  which  is  liable 
to  deliquesce  and  weaken  the  strength  of  the  mortar ; it  should  be  clean,  rather 
coarse,  and  free  from  dirt  and  all  perishable  ingredients.  The  water  should  be 
pure,  fresh,  and,  if  possible,  free  from  fixed  air. 


SECTION  IX.  — Co.MMON  Mortar  and  Cement. 


OF  COMMON  MORTAR  AND  CEMENT. 


63 


The  proportions  of  lime  and  sand  to  each  other  are  varied  in  different  places ; 
the  amount  of  sand,  however,  always  exceeds  that  of  lime.  The  more  sand  that 
can  be  incorporated  with  the  lime,  the  better,  provided  the  necessary  degree  of 
plasticity  is  preserved  ; for  the  mortar  becomes  stronger,  and  it  also  sets,  or  con- 
solidates more  quickly,  when  the  lime  and  water  are  less  in  quantity  and  more 
subdivided.  From  two  to  four  parts  of  sand  are  commonly  used  to  one  of  lime, 
according  to  the  quality  of  the  lime  and  the  labor  bestowed  upon  it.  The  more 
pure  the  lime  is,  and  the  more  thoroughly  it  is  beaten  or  worked  over,  the  more 
sand  it  will  take  up,  and  the  more  firm  and  durable  does  it  become. 


SECTION  X. 

The  ancient  masons  were  so  very  scrupulous  in  the  process  of  mixing  their 
mortar,  that  it  is  said  the  Greeks  kept  ten  men  constantly  employed,  for  a long 
space  of  time,  to  each  basin  ; this  rendered  their  mortar  of  such  prodigious  hard- 
ness, that,  Vetruvius  tells  us,  the  pieces  of  plaster  falling  off  from  old  walls  served 
to  make  tables. 

It  was  a maxim  among  the  old  masons  to  their  laborers,  that  they  should  dilute 
the  mortar  with  the  sweat  of  their  brows ; that  is,  labor  a long  time,  instead  of 
drowning  it  with  w'ater,  to  have  it  done  the  sooner. 

The  weakness  of  modern  mortar  compared  to  the  ancient  is  a common  sub- 
ject of  regret ; and  many  ingenious  men  take  it  for  granted,  that  the  process 
used  by  the  Roman  architects  in  preparing  their  mortar  is  one  of  those  arts  which 
are  now  lost,  and  have  employed  themselves  in  making  experiments  for  its 
recovery. 

But  the  characteristic  of  all  modern  artists,  builders  among  the  rest,  seems  to 
be,  to  spare  their  time  and  labor  as  much  as  possible,  and  to  increase  the  quanti- 
ty of  the  article  they  produce,  without  much  regard  to  goodness  ; and  perhaps 
there  is  no  manufacture  in  which  it  is  so  remarkably  exemplified  as  in  the  prepa- 
ration of  common  mortar. 


SECTION  XL 

Mr.  Doffie  gives  the  following  method  of  making  mortar  impenetrable  to  moist- 
ure, acquiring  great  hardness,  and  exceedingly  durable,  which  was  discovered  by 
a gentleman  of  Neufchatel.  Take  of  unslacked  lime  and  of  fine  sand,  in  the  pro- 
portion of  one  part  of  lime  to  three  of  sand,  as  much  as  a laborer  can  well  manage 


64 


PRACTICAL  MASONRY. 


at  once ; and  then,  adding  water  gradually,  mix  the  whole  well  together  with  a 
trowel,  till  it  be  rendered  to  the  consistency  of  mortar.  Apply  it  immediately, 
while  it  is  hot,  to  the  purpose  either  of  mortar  as  a cement  to  brick  or  stone,  or 
of  plaster  to  the  surface  of  any  building.  It  will  then  ferment  for  some  days,  in 
drier  places,  and  afterwards  gradually  concrete  or  set,  and  become  hard  ; but  in 
a moist  place  it  will  continue  soft  for  three  weeks  or  more ; though  it  will  at 
length  obtain  a firm  consistence,  even  if  water  have  such  access  to  it  as  to  keep 
the  surface  wet  the  whole  time.  After  this  it  will  acquire  a stone-like  hardness, 
and  resist  all  moisture.  The  perfection  of  this  mortar  depends  on  the  ingredients 
being  thoroughly  blended  together ; and  the  mixture  being  applied  immediately 
after  to  the  place  where  it  is  wanted.  The  lime  for  this  mortar  must  be  made  of 
hard  limestone,  shells,  or  marl ; and  the  stronger  it  is,  the  better  the  mortar  will 
be.  When  a very  great  hardness  and  firmness  are  requisite  in  this  mortar,  the 
using  of  skimmed  milk  instead  of  water,  either  wholly  or  in  part,  will  produce  the 
desired  effect. 


SECTION  XII.  — Monsieur  Loriat’s  Mortar. 

Monsieur  LoriaVs  Mortar,  the  method  of  making  which  was  announced  by 
order  of  his  Majesty,  at  Paris,  in  1774,  is  made  in  the  following  manner:  — 
Take  one  part  of  brick  dust,  finely  sifted,  two  parts  of  fine  river-sand,  screened, 
and  as  much  old  slacked  lime  as  may  be  sufficient  to  form  mortar  with  water,  in 
the  usual  method,  but  so  wet  as  to  serve  for  the  slacking  of  as  much  powdered 
quicklime  as  amounts  to  one  fourth  of  the  whole  quantity  of  brick-dust  and  sand. 
When  the  materials  are  well  mixed,  employ  the  composition  quickly,  as  the  least 
delay  may  render  the  application  imperfect,  or  impossible.  Another  method  of 
making  this  compound  is,  to  make  a mixture  of  the  dry  materials  that  is,  of  the 
sand,  brick-dust,  and  powdered  quicklime,  in  the  prescribed  proportion  ; which 
mixture  may  be  put  into  sacks,  each  containing  a quantity  sufficient  for  one  or 
two  troughs  of  mortar.  The  above-mentioned  old  slacked  lime  and  water  being 
prepared  apart,  the  mixture  is  to  be  made  in  the  manner  of  plaster,  at  the  instant 
when  it  is  wanted,  and  is  to  be  well  chafed  with  the  trowel. 


METHOD  OF  MAKING  MORTAR. 


65 


SECTION  XIII. 

Dr.  Higgijvs  has  made  a variety  of  experiments,  in  consequence  of  the  mod- 
ern discoveries  relating  to  fixed  air,  for  the  purpose  of  improving  mortar  used  in 
buildings.  According  to  this  author,  the  perfection  of  lime,  prepared  for  the  pur- 
pose of  making  mortar,  consists  chiefly  in  its  being  totally  deprived  of  its  fixed 
air.  And  as  lime  very  quickly  imbibes  fixed  air,  when  exposed  to  the  atmos- 
phere, it  should  be  applied  to  use  as  soon  as  possible  after  it  is  prepared. 

From  the  experiments  of  the  same  author,  made  with  a view  to  ascertain  the 
best  relative  proportions  of  lime,  sand,  and  water,  in  the  making  of  mortar,  it 
appeared  that  those  specimens  were  the  best  which  contained  one  part  of  lime  in 
seven  of  sand;  for  those  which  contained  less  lime,  and  were  too  short  while  fresh, 
were  more  easily  cut  and  broken,  and  were  pervious  to  water ; and  those  which 
contained  more  lime,  although  they  were  closer  in  grain,  did  not  harden  so  soon, 
or  to  so  great  a degree,  even  when  they  escaped  cracking  by  lying  in  the  shade 
to  dry  slowly. 

Dr.  Higgins  has  also  shown,  that  though  the  setting  of  mortar,  as  it  is  called,  is 
chiefly  owing  to  its  drying,  yet  its  induration,  or  its  acquiring  a stony  hardness, 
is  not  caused  by  its  drying,  as  has  been  supposed,  but  depends  principally  on  its 
acquiring  carbonic  acid,  or  fixed  air  from  the  atmosphere.  In  order  to  the  great- 
est induration  of  mortar,  therefore,  it  must  be  suffered  to  dry  gently,  and  set ; the 
drying  must  be  effected  by  temperate  air,  and  not  accelerated  by  the  heat  of  the 
sun,  or  fire.  It  must  not  be  wet  soon  after  it  sets ; and  afterwards,  it  ought  to 
be  protected  from  wet  as  much  as  possible,  until  it  is  completely  indurated.  The 
same  author  describes  a cement,  or  stucco,  of  his  own  invention,  for  incrustations 
external  and  internal,  of  very  great  hardness,  for  which  he  obtained  letters  patent. 
As  for  the  materials  of  which  it  is  made,  drift  sand,  or  quarry  sand,  consisting 
chiefly  of  hard,  quartzose,  flat-faced  grains,  with  sharp  angles,  free  from  clay,  salts, 
&.C.,  is  to  be  preferred.  The  sand  is  to  be  sifted  in  streaming  clear  water, 
through  a sieve  which  shall  give  passage  to  all  such  grains  as  do  not  exceed  one 
sixteenth  of  an  inch  in  diameter ; and  the  stream  of  water,  and  sifting,  are  to  be 
so  regulated,  that  all  the  finer  sand,  together  with  clay  and  other  matter  lighter 
than  sand,  may  be  washed  away  with  the  stream.  While  the  purer  and  coarser 
sand,  which  passes  through  the  sieve,  subsides  in  a convenient  receptacle,  the 
coarse  rubbish  in  the  sieve  is  to  be  rejected.  The  subsiding  sand  is  then  washed 
in  clean  streaming  water,  through  a finer  sieve,  so  as  to  farther  cleanse  it,  and 
sorted  into  two  parcels,  — a coarser,  which  will  remain  in  the  sieve,  which  is  to 

9 


66 


PRACTICAL  MASONRY. 


give  passage  only  to  such  grains  as  are  less  than  one  thirteenth  of  an  inch  in 
diameter,  and  which  is  to  be  kept  apart  under  the  name  of  coarse  sand  ; and  a 
finer  which  will  pass  through  the  sieve,  and  subside  in  the  w^ater,  and  which  is  to 
be  saved  apart  under  the  name  of  fine  sand.  These  are  to  be  dried  separately, 
either  in  the  sun  or  on  a clean  iron  plate,  set  on  a convenient  surface,  in  the  man- 
ner of  a sand  heat.  The  lime  to  be  chosen  should  be  stone-lime,  w'hich  heats 
the  most  in  slacking,  and  slacks  the  quickest  w'hen  duly  watered ; which  is  the 
freshest  made,  and  most  closely  kept.  Let  this  lime  be  put  into  a brass-wired, 
fine  sieve,  to  the  quantity  of  fourteen  pounds.  Let  the  lime  be  slacked  by  plunging 
it  in  a butt,  filled  with  soft  w'ater,  and  raising  it  out  quickly,  and  suffering  it  to 
heat  and  fume,  and  by  repeating  this  plunging  and  raising  alternately,  and  agitat- 
ing the  lime,  until  it  be  made  to  pass  through  the  sieve.  Reject  the  part  of  the 
lime  that  does  not  easily  pass  through  the  sieve,  and  use  fresh  portions  of  lime 
till  as  many  ounces  have  passed  through  the  sieve  as  there  are  quarts  of  water  in 
the  butt.  Let  the  w'ater  thus  impregnated  stand  in  the  butt,  close  covered,  until 
it  becomes  clear ; and  through  wooden  cocks,  placed  at  different  heights  in  the 
butt,  draw  oft'  the  clear  liquor,  as  fast  and  as  low  as  the  lime  subsides,  for  use. 
This  clear  liquor  is  called  the  cementing  liquor. 

Let  fifty-six  pounds  of  the  aforesaid  chosen  lime  be  slacked,  by  gradually 
sprinkling  on  it  the  cementing  liquor,  in  a close,  clean  place.  Let  the  slacked 
part  be  immediately  sifted  through  the  fine  brass-wired  sieve.  Let  the  lime 
which  passes  be  used  instantly,  or  kept  in  air-tight  vessels,  and  let  the  part  of  the 
lime  which  does  not  pass  through  the  sieve  be  rejected  ; the  other  part  is  called 
purified  lime. 

Let  bone-ashes  be  prepared  in  the  usual  manner,  by  grinding  the  whitest  burnt 
bones  ; but  they  should  be  finely  sifted. 

Having  thus  prepared  the  materials,  take  fifty-six  pounds  of  the  coarse  sand, 
and  forty-two  pounds  of  the  fine  sand  ; mix  them  on  a large  plank  of  hard  wood, 
placed  horizontally.  Then  spread  the  sand  so  that  it  may  stand  at  the  height  of 
six  inches,  with  a flat  surface  on  the  plank  ; wet  it  with  the  cementing  liquor ; to 
the  wetted  sand  add  fourteen  pounds  of  the  purified  lime,  in  several  successive 
portions,  mixing  and  beating  them  together ; then  add  fourteen  pounds  of  the 
bone-ashes  in  successive  portions,  mixing  and  beating  them  all  together.  This 
Dr.  Higgins  calls  the  water  cement,  coarse-grained,  which  is  to  be  applied  in 
building,  pointing,  plastering,  stuccoing,  &.c.  Observing  to  work  it  expeditiously 
in  all  cases,  and  in  stuccoing  to  lay  it  on  by  sliding  the  trowel  upwards  upon  it ; 
to  w'ell  wet  the  materials  used  with  it,  or  the  ground  on  which  it  is  laid,  with  the 
cementing  liquor,  at  the  time  of  laying  it  on ; and  to  use  the  cementing  liquor 
for  moistening  the  cement  and  facilitating  the  floating  of  it. 


METHOD  OF  MAKING  MORTAR. 


67 


A cement  of  a finer  texture  may  be  made,  b}’  using  ninety  pounds  of  the  fine 
sand,  and  fifteen  pounds  of  lime,  with  bone-ashes  and  cementing  liquor.  This  is 
called  water  cement,  fine-grained,  and  is  used  in  giving  the  last  coating  or  finish 
to  anv  work  intended  to  imitate  the  finer-grained  stones  or  stucco. 

For  a cheaper  or  coarser  cement,  take  of  coarse  sand  fifty-six  pounds,  of  the 
foregoing  coarse  sand  twenty-eight  pounds,  and  of  the  finer  sand  fourteen  pounds  ; 
and  after  mixing  and  wetting  these  with  the  cementing  liquor,  add  fourteen 
pounds  of  the  purified  lime,  and  then  as  much  bone-ashes,  mixing  them  together. 

The  water  cement  above  described  is  applicable  to  forming  artificial  stone,  by 
making  alternate  layers  of  the  cement  and  of  Hint,  hard  stone,  or  brick,  in  moulds 
of  the  figure  of  the  intended  stone,  and  by  exposing  the  masses  so  formed  to  the 
open  air  to  harden.  When  the  cement  is  required  for  water  fences,  two  thirds 
of  the  bone-ashes  are  to  be  omitted,  and  in  their  stead  an  equal  measure  of  pow- 
dered terras  (see  Terras)  is  to  be  used.  When  the  cement  is  required  of  the 
finest  grain,  or  in  a fluid  form,  so  that  it  may  be  applied  with  a brush.  Hint  pow- 
der, or  the  powder  of  any  quartzose,  or  hard,  earthy  substance,  may  be  used  in  the 
place  of  sand,  so  that  the  powder  shall  not  be  more  than  six  times  the  weight  of 
the  lime,  nor  less  than  four  times  its  weight.  For  inside  work  the  admixture  of 
hair  with  the  cement  is  useful. 

When  a fragment  of  a worked  stone  is,  by  accident  or  otherwise,  broken  ofl', 
it  may  be  united  with  a firmness  suflicient  to  resist  a considerable  degree  of 
force  by  a cement  made  of  five  parts  gum  shellac,  and  one  part  of  Burgundy  \‘ 

pitch,  incorporated  together  in  an  iron  vessel,  over  a slow  fire.  The  cement, 
while  hot,  should  be  applied  to  the  stone,  raised  also  to  a moderate  degree  of 
heat.  In  order  that  the  cement  should  not  cool  too  rapidly,  a piece  of  iron  should 
be  heated,  and  laid  on  the  stone,  and  the  whole  suHered  to  cool  gradually  togeth- 
er. The  cement  may  be  made  to  assume  the  color  of  the  stone  to  be  united,  by 
mixing  with  it  a portion  of  the  stone  itself,  reduced  to  a fine  powder.  Stones 
thus  united  may  afterwards  be  smoothed  by  gentle  hammering,  while  the  fracture 
is  not  perceptible,  except  by  very  close  examination. 


SECTION  XIV. 

Although  a well  made  moi-tar,  composed  merely  of  sand  and  lime,  allowed 
to  dry,  becomes  impervious  to  water,  so  as  to  serve  for  the  lining  of  reservoirs 
and  aqueducts;  yet  if  the  circumstances  of  the  building  are  such  as  to  render  it 
impracticable  to  keep  out  the  water,  whether  fresh  or  salt,  a suflicient  length  of 
time,  the  use  of  common  mortar  must  be  abandoned. 


68 


PRACTICAL  MASONRY. 


Among  the  nations  of  antiquity,  the  Romans  appear  to  have  been  the  only  peo- 
ple who  have  practised  building  in  water,  and  especially  in  the  sea,  to  any  ex- 
tent. The  bays  of  Baiae,  of  Pozzuolo,  and  of  Cumae,  from  their  coolness  and  sa- 
lubrity of  situation,  were  the  fashionable  resorts  of  the  wealthier  Romans,  during 
the  summer  months ; who  not  only  erected  their  villas  and  baths  as  near  the  shore 
as  possible,  but  constructed  moles  and  formed  small  islands  in  the  more  sheltered 
parts  of  these  bays  ; on  which,  for  the  sake  of  the  grateful  coolness,  they  built 
their  summer-houses  and  pavilions.  They  were  enabled  to  build  thus  securely 
by  the  discovery,  at  the  town  of  Puteoli,  of  an  earthy  substance,  which  was  called 
pulvis  puteolanus,  Puteolan  powder,  or,  as  it  is  now  called,  puzzolana  (which  see). 
The  only  preparation  which  this  substance  undergoes  is  that  of  pounding  and 
sifting,  by  which  it  is  reduced  to  a coarse  powder ; in  this  state,  being  thoroughly 
beaten  up  with  lime,  either  with  or  without  sand,  it  forms  a mass  of  remarkable 
tenacity,  which  speedily  sets,  under  water,  and  becomes,  at  least,  as  hard  as  good 
freestone. 

Limes  which  contain  a portion  of  clay,  or  argillaceous  matter,  have  also  the 
property  of  forming  a mortar,  which  hardens  under  water.  A composition  formed 
of  two  bushels  of  clayey  lime,  one  bushel  of  puzzolana,  and  three  of  clean  sand, 
the  whole  being  well  beaten  together,  make  a good  water  cement. 

The  terras  which  is  so  much  used  in  Holland  is  a preparation  of  a species  of 
basalt  (which  see),  by  calcination.  It  possesses  the  property,  when  mixed  with 
lime,  of  forming  a water  cement,  not  inferior  to  puzzolana.  Perhaps  common 
greenstone  and  other  substances  may  be  found  to  answer  the  same  purposes. 

The  materials  of  terras  mortar,  generally  used  in  the  construction  of  the  best 
water  work,  are  one  measure  of  quicklime,  or  two  measures  of  slacked  lime,  in 
the  dry  powder,  mixed  with  one  measure  of  terras,  well  beaten  together  to  the 
consistency  of  paste,  using  as  little  water  as  possible. 

Another  kind  almost  equally  good,  and  considerably  cheaper,  is  made  of  two 
measures  of  slacked  lime,  one  of  terras,  and  three  of  coarse  sand  ; it  requires  to 
be  beaten  longer  than  the  foregoing,  and  produces  three  measures  and  a half  of 
excellent  mortar.  When  the  building  is  constructed  of  rough,  irregular  stones, 
where  cavities  and  large  joints  are  to  be  filled  up  with  cement,  the  pebble  or 
coarse-sand  mortar  may  be  most  advantageously  applied ; this  was  a favorite 
mode  of  constructing  among  the  Romans,  and  has  been  much  used  since.  Peb- 
ble mortar  will  be  found  of  a sufficient  compactness,  if  composed  of  two  meas- 
ures of  slacked,  argillaceous  lime,  half  a measure  of  terras,  or  puzzolana,  and  one 
measure  of  coarse  sand,  one  of  fine  sand,  and  four  of  small  pebbles,  screened  and 
washed.  It  is  only  under  water  that  terras  mortar  sets  well. 

The  scales  produced  by  hammering  red-hot  iron,  which  may  be  procured  at 


OF  STUCCO. 


69 


the  forges  and  blacksmiths’  shops,  have  been  long  knowm  as  an  excellent  materi- 
al in  water  cements.  The  scales  being  pulverized  and  sifted,  and  incorporated 
with  lime,  are  found  to  produce  a cement  equally  powerful  with  puzzolana  mor- 
tar, if  employed  in  the  same  quantity. 

Fresh-made  mortar,  if  kept  under  ground,  in  considerable  masses,  may  be 
preserved  for  a great  length  of  time,  and  the  older  it  is  before  it  is  used,  the  bet- 
ter it  has  been  thought  to  be. 

Pliny  informs  us  that  the  ancient  Roman  laws  prohibited  builders  from  using 
mortar  that  was  less  than  three  years  old,  and  a similar  law  prevails  in  Vienna. 


SECTION  XV.  — Stucco. 

This  is  a composition  of  white  marble,  pulverized  and  mixed  with  plaster,  or 
lime,  the  whole  sifted  and  wrought  up  with  water,  to  be  used  like  common  plas- 
ter. 

Of  this  are  made  statues,  busts,  basso-relievos,  and  other  ornaments  of  archi- 
tecture. 

A stucco,  for  walls,  &,c.,  may  be  formed  of  the  grout,  or  putty,  made  of  good 
stone-lime,  or  the  lime  of  cockle-shells,  which  is  better,  properly  tempered  and 
sufficiently  beat,  mixed  with  sharp  grit  sand,  in  a proportion  which  depends  on 
the  strength  of  the  lime.  Drift-sand  is  best  for  this  purpose,  and  it  will  derive 
advantage  from  being  dried  on  an  iron  plate  or  kiln,  so  as  not  to  burn  ; thus  the 
mortar  would  be  discolored.  When  this  is  properly  compounded,  it  should  be 
put  in  small  parcels  against  walls,  or  otherwise,  to  mellow,  as  the  workmen  term 
it ; reduced  again  to  soft  putty,  or  paste,  and  spread  thin  on  the  walls  without 
any  under  coat,  and  well  trowelled.  A succeeding  coat  should  be  laid  on  before 
the  first  is  quite  dry,  which  will  prevent  points  of  brick-work  appearing  through 
it.  Much  depends  on  the  workman  giving  sufficient  labor,  and  trowelling  it 
down.  If  this  stucco,  when  dry,  be  laid  over  with  boiling  linseed  oil,  it  will  last  a 
long  time,  and  not  be  liable,  when  once  hardened,  to  the  accidents  to  which  com- 
mon stucco  is  liable. 


SECTION  XVI. 

Adam's  Oil  Cement,  or  Stucco,  is  prepared  in  the  following  manner.  For  the 
first  coat  take  twenty-one  pounds  of  fine  whiting,  or  oyster-shells,  or  any  other 


70 


PRACTICAL  MASONRY. 


sea-shells  calcined,  or  plaster  of  Paris,  or  any  calcareous  material  calcined  and 
pounded,  or  any  absorbent  materials  whatever,  proper  for  the  purpose ; add 
white  or  red  lead  at  pleasure,  deducting  from  the  other  absorbent  materials  in 
proportion  for  the  white  or  red  lead  added  ; to  which  put  four  quarts,  beer  meas- 
ure, of  oil,  and  mix  them  together  with  a grinding  mill  or  any  levigating  machine; 
and  afterwards  mix  and  beat  up  the  same  well  with  twenty-eight  quarts,  beer 
measure,  of  any  sand  or  gravel,  or  of  both,  mixed  and  sifted,  or  of  marble  or  stone 
pounded,  or  of  brick-dust,  or  of  any  kind  of  metallic  or  mineral  powders,  or  of 
any  solid  material  whatever,  fit  for  the  purpose. 

For  the  second  coat  take  sixteen  pounds  and  a half  of  superfine  whiting,  or 
oyster-shells,  or  any  sea-shells  calcined,  &c.,  as  for  the  first  coat ; add  sixteen 
pounds  and  a half  of  white  or  red  lead,  to  which  put  six  quarts  and  a half  of  oil, 
wine  measure,  and  mix  them  together  as  before.  Afterwards  mix  and  beat  up 
the  same  well  with  thirty  quarts,  wine  measure,  of  fine  sand  or  gravel  sifted,  or 
stone  or  marble  pounded,  or  pyrites,  or  any  kind  of  metallic  or  mineral  powder, 
&LC.  This  composition  requires  a greater  proportion  of  sand,  gravel,  or  other  sol- 
ids, according  to  the  nature  of  the  work,  or  the  uses  to  which  it  is  to  be  applied. 
If  it  be  required  to  have  the  composition  colored,  add  to  the  above  ingredients 
such  a portion  of  painters’  colors  as  will  be  necessary  to  give  the  tint  or  color 
required.  In  making  the  composition,  the  best  linseed,  or  hemp-seed,  or  other 
oils,  proper  for  the  purpose,  are  to  be  used,  boiled  or  raw,  with  drying  ingre- 
dients, as  the  nature  of  the  work,  the  season,  or  the  climate  requires  ; and  in 
some  cases  beeswax  may  be  substituted  in  place  of  oil.  All  the  absorbent  and 
solid  materials  must  be  kiln-dried.  If  the  composition  is  not  to  be  any  other 
color  than  white,  the  lead  may  be  omitted,  by  taking  the  full  proportion  of  the 
other  absorbents  ; and  also  white  or  red  lead  may  be  substituted  alone,  instead  of 
any  absorbent  material. 

The  first  coat  of  this  composition  is  to  be  laid  on  with  a trowel,  and  floated  to 
an  even  surface,  with  a rule  or  handle  float.  The  second  coat,  after  it  is  laid 
on  with  a trowel,  when  the  other  is  nearly  dry,  should  be  worked  down  and 
smoothed,  with  floats  edged  with  horn,  or  any  hard,  smooth  substance,  that  does 
not  stain.  It  may  be  proper,  previously  to  laying  on  the  composition,  to  mois- 
ten the  surface  on  which  it  is  to  be  laid,  by  a brush,  with  the  same  kind  of  oil 
or  ingredients  which  pass  through  the  levigating  machine,  reduced  to  a more 
liquid  state,  in  order  to  make  the  composition  adhere  the  better.  This  compo- 
sition admits  of  being  modelled,  or  cast  in  moulds,  in  the  same  manner  as  plas- 
terers or  statuaries  model  or  cast  their  stucco-work.  It  also  admits  of  being 
painted  upon,  and  adorned  with  landscape,  or  ornamental,  or  figure  painting,  as 
well  as  plain  painting. 


OF  SCAGLIOLA. 


71 


SECTION  XVII.  — ScAGLIOLA. 

This  composition  has,  of  late  years,  begun  to  be  much  employed  in  the  inte- 
riors of  mansions,  and  may  be  applied  not  only  to  columns,  their  capitals  and 
bases,  but  also  to  the  panelling  of  walls,  &c. 

The  formation  of  columns,  &c.,  in  scagliola,  is  a distinct  branch  of  plastering. 
It  was  first  invented  in  Italy,  thence  carried  to  France,  and  afterwards  to  Eng- 
land. The  credit  of  its  introduction  into  England  belongs  to  Henry  Holland, 
Esq.,  architect. 

He  procured  artists  from  Paris  to  perform  w'orks  with  this  composition  at  Carl- 
ton Palace,  some  of  whom,  finding  a considerable  demand  for  their  productions, 
remained  in  England,  from  whom  British  workmen  learnt  the  art,  and  have  since 
brought  it  to  the  greatest  perfection. 

Scagliola  is  a composition  of  plaster  of  Paris  and  earthy  colors,  or  any  colors 
which  will  withstand  the  action  of  an  alkali.  In  its  manufacture,  the  ground  or 
predominating  color  is  first  mixed  to  the  desired  tint,  and  the  other  colors  intend- 
ed to  be  introduced  must  be  mixed  separately,  with  a portion  of  clear  size,  and  a 
little  spirits  of  turpentine,  to  facilitate  the  drying. 

If,  in  the  marble  intended  to  be  imitated,  the  colors  blend  gradually  into  each 
other,  as  in  Sienna  and  the  others  generally  executed,  the  imitation  must  be 
formed  while  the  colors  are  in  a soft  state,  by  putting  the  ground  mixture  into  a 
large  trough,  and  adding  the  different  colors  in  a proportion  and  a taste  which  can 
alone  be  acquired  by  experience. 

If,  on  the  contrary,  the  distinction  between  the  colors  is  strongly  marked,  the 
secondary  colors  must  be  allowed  to  set  nearly  hard,  broken  into  small  pieces, 
and  added  to  the  ground  mixture,  which  must  be  kepi  in  the  trough  in  a soft 
state,  as  before  mentioned. 


SECTION  XVIII.  — Manner  of  forming  Columns  or  Pilasters  in  Scagliola. 

When  the  architect  has  furnished  the  drawing  exhibiting  the  diameter  of  the 
shaft,  a cradle  is  made  of  wood  about  two  and  one  half  inches  less  in  diameter 
than  the  projected  column.  The  circumference  of  this  cradle  being  lathed  with 
double  laths,  as  in  common  plastering,  must  be  covered  with  a pricking-up  coat 
of  plaster,  gauged  with  very  thin  size,  in  order  to  harden  it. 

The  pricking-up  coat,  after  being  completely  set,  must  be  well  soaked  with 


72 


PRACTICAL  MASONRY. 


water.  The  composition  must  be  then  taken  from  the  trough,  flattened  into 
cakes  about  eight  inches  square,  applied  to  the  column,  and  well  beat  on  with  a 
wooden  beater  and  small  gauging-trowel.  In  this  state  it  must  remain  until  per- 
fectly dry,  when  the  protuberances  may  be  taken  off,  with  a plane.  The  column 
must  then  be  put  in  the  lathe  and  turned  to  the  size  required.  This  operation 
being  finished,  it  will  have  a porous  appearance,  which  must  be  obviated  by  the 
application  of  a thick  wash,  and  scraping  it  with  steel  scrapers  until  it  assumes 
the  surface  of  real  marble,  when  it  will  be  fit  for  polishing,  which  must  be  effect- 
ed by  first  using  pumice-stone,  at  the  same  time  cleansing  it  with  a wet  sponge, 
and  afterwards  with  Tripoli  powder  and  charcoal.  After  going  over  the  whole 
with  a piece  of  white  glove-leather,  dipped  in  a mixture  of  Tripoli  powder  and  oil 
of  olives,  the  process  must  be  finished  by  the  application  of  pure  oil. 

White  scagliola  is  simply  a mixture  of  plaster  of  Paris  and  mineral  green,  the 
manner  of  using  it  being  the  same  as  above  described. 


SECTION  XIX.  — Modelling  for  Stucco  or  Plaster  of  Paris. 

The  whole  of  the  ornaments  cast  in  plaster  of  Paris  are  previously  modelled  in 
clay,  which  method  has  of  late  years  almost  entirely  supplanted  the  process  of 
working  the  ornaments  in  their  places  by  hand. 

Large  works,  such  as  angle-pieces  and  foliage  for  ceilings,  require  more  judg- 
ment than  enriched  mouldings,  such  as  ogees  or  ovelos,  sthe  eye  of  the  model- 
ler in  the  former  case  being  his  only  guide,  whereas,  in  the  mouldings,  the  com- 
passes are  found  of  essential  service.  For  example,  in  the  moulding  of  an 
ogee,  only  one  of  the  divisions  is  required  to  be  modelled  in  clay,  which  may  be 
effected  by  procuring  a templet  exactly  corresponding  with  the  profile  of  the 
moulding,  and  running  a small  portion  of  the  moulding  out  with  it  in  clay,  in 
a small  case  of  wood  adapted  to  the  purpose.  The  design  of  the  ornament  is 
then  marked  on  the  clay,  and  moulded  to  its  peculiar  form  by  the  use  of  tools 
made  of  ebony  and  box,  and  finely  polished  with  brass  tools.  When  finished  in 
the  modelling,  it  is  moulded  in  wax,  and  a sufficient  number  cast  and  fixed 
together  to  a length  varying  from  eight  inches  to  one  foot,  and  afterwards  cleaned 
up  and  corrected  with  steel  and  brass  tools.  This  piece  of  ornament,  after  being 
properly  corrected,  is  called  the  original,  as  an  unlimited  number  of  moulds  may  be 
taken  from  it.  In  moulding  angle-pieces  it  is  necessary  to  run  out  a sufficient 
quantity  of  the  plain  moulding  in  putty  and  plaster  to  the  exact  form  of  the  angle. 
The  embellishments  are  then  modelled  on  the  mouldings,  and  also  moulded  there- 


OF  THE  MOULDING  OF  ORNAMENTS. 


73 


on,  the  mouldings  forming  a ground  for  the  ornaments,  so  that,  after  being  cast, 
they  will  exactly  fit  the  mouldings  when  fixed  in  their  proper  situations  on  the 
ceiling. 


SECTION  XX Moulding  of  Ornaments. 

There  are  two  methods  of  moulding  practised  by  plasterers,  namely,  moulding 
in  wax  and  moulding  in  plaster ; the  former  is  applied  to  all  kinds  of  cornice  en- 
richments, as  friezes,  soffits,  ogees,  ovolos,  &c.,  and  also  to  centre-flowers  and 
angle-pieces;  the  latter  is  generally  employed  for  works  of  large  dimension, 
which,  from  the  manner  in  which  they  are  under  cut,  are  not  easily  cast  in  wax 
moulds,  as  coats  of  arms,  trophies,  and  plain  capitals  attached  to  trusses ; it  may 
also  be  applied  to  works  in  Roman  cement,  such  as  balustrades,  heads,  &c.  In 
moulding  in  wax,  the  clay  model  must,  in  the  first  place,  be  well  oiled  with  sweet 
oil,  and  a fence  of  clay  put  round  it,  to  prevent  the  liquid  wax  from  escaping,  after 
which  a sufficient  quantity  of  wax  and  rosin  must  be  dissolved  together,  which, 
when  lukewarm,  must  be  poured  over  the  model,  until  it  is  completely  covered. 
When  the  wax  is  sufficiently  set,  the  whole  must  be  immersed  in  water,  which 
will  cause  it  to  leave  more  readily ; after  which,  the  clay  being  all  washed  out  of 
the  mould,  it  will  be  fit  for  casting  in. 

This  method  will  be  found  sufficient  where  a face  mould  only  is  required,  but 
when  what  is  termed  a back-and -front  is  wanted,  as  is  the  case  in  all  leaves  for 
centre-flowers,  it  is  requisite  to  cut  the  front  plaster-cast  back,  so  that  the  ruffling 
will  show  distinctly,  and  afterwards  to  soak  it  in  water.  The  leaf  must  then  be 
backed  up  all  round,  within  one  sixteenth  of  an  inch  of  the  edge,  with  a sub- 
stance of  clay,  an  inch  wide,  in  which  rivets  must  be  inserted.  The  leaf  being 
freed  from  all  particles  of  water  which  may  remain  on  the  surface,  the  clay  must 
be  well  oiled.  A fence  of  clay  is  then  put  round  the  whole,  and  the  wax  poured 
on,  which,  after  remaining  until  quite  hard,  must  be  turned  upside  down,  and  the 
clay  all  removed  from  it,  when  the  wax  must  be  oiled  or  the  whole  brushed  over 
with  a little  liquid  clay.  Another  quantity  of  wax  must  be  prepared,  and,  when 
almost  cold,  poured  over  the  first,  which  will  form  the  back  mould ; a fence  of 
clay  being  provided,  is  put  round  to  prevent  the  wax  from  escaping.  When  this 
mass  is  sufficiently  set,  the  two  parts  may  be  disunited,  and  the  plaster-leaf  re- 
moved, thus  forming  two  moulds,  the  one  for  casting  the  back,  and  the  other  the 
front  of  the  leaf.  This  manner  of  moulding  is  also  used  for  all  kinds  of  foliages 
which  need  much  relief. 


10 


74 


PRACTICAL  MASONRY. 


SECTION  XXL  — Moulding  in  Plaster. 

Ijv  moulding  in  plaster,  the  same  as  in  wax,  the  clay  model  must  be  oiled  with 
sweet  oil,  but  the  plaster  must  be  laid  (not  too  soft)  by  one  piece  at  a time,  form- 
ing the  joints,  and  fitting  them  to  each  other,  in  such  situations  as  the  skill  of  the 
workman  may  suggest.  After  having  completely  covered  the  model  with  pieces, 
the  whole  must  be  removed,  and,  when  perfectly  dry,  soaked  in  boiled  linseed  oil. 
The  various  parts  of  the  mould,  being  well  saturated  with  oil  and  quite  dry,  are 
fit  for  use,  and  may  be  oiled,  ready  for  casting,  with  sweet  oil,  in  the  same  man- 
ner as  wax  moulds. 

Casting  in  Plaster.  The  moulds  being  prepared  and  properly  cleansed,  are 
oiled  in  the  way  above  mentioned.  A sufficient  quantity  of  plaster  of  Paris,  being 
mixed  with  water  to  a semi-fluid  state,  is  well  dubbed  into  the  mould  with  a 
small  brush,  which,  after  remaining  a short  time,  is  floated  off  flush  with  the  rim 
of  the  mould.  The  plaster  being  set,  the  impression  is  taken  from  the  mould  by 
means  of  pressing  the  wax  gently  with  the  hands  all  round,  the  heat  of  the  plas- 
ter causing  the  mould  to  yield.  The  ornaments,  after  being  taken  from  the  mould, 
are  cleaned  up  and  cut  with  a trimming-knife  to  the  proper  joints,  ready  for  the 
workman  to  fix  in  the  places  intended  for  their  reception. 

Friezes  and  basso-relievos  should  always  be  cut  with  a half-inch  ground  at 
their  backs,  which  serves  to  strengthen  and  secure  their  proportions. 


SECTION  XXII.  — Fixing  Ornaments. 

When  the  enrichments  about  to  be  fixed  are  small  in  size,  they  may  be  fixed 
in  the  grooves  or  indents  prepared  for  them  with  putty  well  gauged  with  plaster; 
but  when  the  ornaments  are  of  a weighty  description,  it  becomes  necessary  to 
use  fine  stuff",  and  to  cut  away  the  plain  surface  of  the  work  as  far  as  the  lathing. 
The  place  so  cut  away  is  then  filled  with  gauged  fine  stuff",  and  the  cast,  being 
well  scratched  on  the  back  in  the  form  of  a dovetail,  must  also  have  a portion  of 
fine  stuff"  laid  on  it  when  it  is  placed  in  its  proper  position,  and  pressed  to  the 
work,  so  that  they  may  both  incorporate.  When  the  ornaments  are  extremely 
heavy,  such  as  coats  of  arms  and  shields,  in  addition  to  the  above  mode,  it  is  in- 
dispensably necessary  to  have  recourse  to  large  screws,  which  must  pass  through 
the  cast  work  into  the  timber. 


OF  STUCCO  CORNICES. 


75 


SECTION  XXIII.  — Stucco  Cornices. 

Previous  to  the  operation  of  forming  the  cornice,  it  should  be  the  practice  of 
the  plasterer  to  examine  the  drawings,  before  the  preparation  is  made  for  the 
pricking-up  coat.  When  the  projection  does  not  exceed  seven  or  eight  inches,  it 
is  the  practice,  in  filling  in  or  blocking  with  coarse  stuff,  as  common  plastering 
mortar,  to  fill  within  one  half  or  three  quarters  of  an  inch  of  the  mould,  and  leave 
it  as  rough  as  possible  for  the  putty  to  adhere  to;  but  in  case  the  cornice  should 
project  eight  inches  or  over,  it  is  best  in  most  cases  to  bracket  the  angle  of  the 
ceiling.  First  fit  a piece  of  pasteboard  so  as  to  conform  to  all  the  members  of  a 
section  of  the  drawing,  on  the  outside  of  the  projections.  The  pasteboard  may 
be  pasted  on  to  a thin  plate  of  metal,  of  iron,  copper,  or  steel,  and  by  the  means 
of  files,  &c.,  is  fitted  to  the  details  of  the  mouldings  cut  out  from  the  pasteboard. 
A piece  of  wood  is  fixed  to  the  metallic  mould  about  half  an  inch  thick,  so  bev- 
elled as  not  to  clog  in  the  moulding  of  the  cornice,  leaving  the  edge  of  the  mould 
or  metallic  part  to  project  about  one  half  or  one  quarter  of  an  inch  from  the  wood 
backing.  On  the  top  and  bottom  part  of  the  mould  are  attached  two  slides  of 
wood,  to  keep  the  mould  in  a proper  position  on  the  screeds,  and  at  a right  an- 
gle with  the  wall ; and  sometimes  a mould  is  made  for  the  using  of  coarse  stuff, 
which  is  about  one  eighth  of  an  inch  smaller  in  all  of  its  members  than  the  afore- 
mentioned mould.  Bracketing  is  formed  of  inch -boards,  so  as  to  fall  three  quar- 
ters or  one  inch  within  the  general  projections  of  the  aforesaid  mould,  and  fastened 
up  about  one  foot  apart,  and  properly  latbed,  and  covered  with  a coat  of  coarse 
stuff.  The  cutting  of  moulds  being  completed,  the  ceiling  and  walls  floated  and 
levelled,  the  projection  of  the  cornice  must  be  lined  on  tbe  ceiling,  and  also  its  en- 
croachment on  the  wall.  At  each  line  of  projection,  narrow  screeds  must  be  made, 
with  a very  thin  coat  of  strong  gauged  fine  stuff,  and  perfectly  smoothed  wdth 
the  floating-rule.  In  the  making  of  these  screeds,  much  pains  must  be  taken,  as 
the  correctness  of  the  cornice  depends  upon  the  precaution  used  in  their  formation. 

The  running  rules  properly  adjusted  on  a straight  line,  wooden  strips  about 
three  inches  wide  and  one  half  an  inch  thick  nailed  upon  the  protruding  line  on 
the  wall,  which  has  been  done  round  the  room  for  the  purpose  of  directing  the 
mould  in  forming  the  cornice, — the  aforesaid  preliminaries  being  attended  to,  it  is 
fitted  for  running. 

Running  the  Cornice.  Two  workmen  and  a boy  are  required,  one  to  lay  on  the 
stuff,  and  the  other  to  work  the  mould.  The  hawk-boy  commences  gauging  the 


76 


PRACTICAL  MASONRY. 


coarse  stuff,  which  at  first  must  be  gauged ; one  of  the  workmen  takes  a portion 
of  it  on  his  hawk,  and  plasters  a part  of  it  on  the  place  where  the  cornice  is  to  be ; 
the  other  workman  begins,  by  moving  the  mould  backward  and  forward,  holding 
it  firmly  to  the  ceiling  and  wall,  thus  removing  the  superfluous  stuff ; this  opera- 
tion is  continued  until  the  cornice  is  as  perfectly  formed  as  can  be  with  the  coarse 
stuff.  The  putty  and  plaster  is  then  gauged,  and  the  same  process  pursued  as  in 
the  coarse  stuff,  using  the  fine  mould,  adding  gauged  stuff  until  the  exact  contour 
of  the  cornice  is  formed. 

When  the  cornice  is  very  large,  it  may  be  best  to  run  it  by  using  two  small 
moulds ; one  below,  forming  the  plainer  face  and  bed  mouldings,  and  the  other 
part  forming  the  crown  mouldings,  &c. 

The  mitres  internal  and  external,  as  well  as  breaks  or  small  returns,  are 
formed  afterwards  by  hand,  wuth  small  tools  for  the  purpose. 


SECTION  XXIV.  — Circular  and  Elliptical  Cornices  or  Mouldings. 

This  kind  of  cornice  requires  much  more  labor  than  straight  ones,  but  the 
principal  operation  is  the  same,  except  that  when  they  are  circular  they  must  be 
run  from  a centre,  by  means  of  w'hat  is  called  a gig-stick,  to  which  the  mould  is 
attached ; a hole  being  bored  in  it  exactly  to  the  radius,  w^hich  fits  to  a pin  placed 
exactly  in  the  centre  of  the  circular  moulding.  When  the  mouldings  are  to  de- 
scribe an  ellipsis,  the  most  correct  method  is  to  run  them  from  a trammel,  such 
as  is  used  by  carpenters. 


SECTION  XXV.  — External  Compositions. 

Within  the  last  fifty  years,  great  improvements  have  been  made  in  the  art 
of  plastering  by  the  invention  of  various  compositions  for  the  covering  of  the  ex- 
teriors of  buildings,  such  as  Roman  cement,  terra  cotta,  mastic,  and  Bailey’s  com- 
position. 

These  compositions  are  susceptible  of  being  applied  both  to  the  finishing  a 
plain  surface  to  be  jointed  to  imitate  stone,  and  in  the  formation  of  ornaments  of 
every  description.  On  account  of  their  cheapness,  they  have  given  rise  to  design 
and  much  architectural  display,  w^hich  heretofore  w^as  not  thought  of. 

The  careful  study  of  the  antique  examples  of  architecture,  both  in  Greece 
and  ancient  Rome,  has  also  acted  as  a pow^erful  stimulus  to  the  promotion  of  the 


OF  EXTERNAL  COMPOSITIONS. 


71 


art  of  design,  as  well  as  ornamental  plastering ; more  particularly  in  the  getting 
up  of  Greek  and  Roman  capitals,  the  former  of  which  were,  until  within  the  last 
few'  years,  scarcely  known  in  Europe ; and  the  latter  have  been  most  essentially 
improved  by  reference  to  the  casts  procured  from  the  original,  now^  extant. 

The  invention  of  composition  has,  no  doubt,  been  facilitated  by  the  scarcity  of 
good  stone  in  the  south  part  of  Great  Britian.  Other  parts  and  other  countries 
availing  themselves  of  these  improvements,  have,  in  many  instances,  been  led 
to  farther  study  in  the  arts,  and  it  operates  as  a stimulus  to  the  taste  for 
ornamental  decorations  and  is  of  great  utility  to  the  public  interests  of  this  coun- 
try, although  probably  no  nation  in  the  w'orld  possesses  a greater  variety  of  useful 
building  materials  than  the  United  States  of  America. 

Roman  Cement  or  Compo  was  first  introduced  to  public  notice  by  the  late 
James  Wyatt,  Esq.  It  was  originally  known  as  Parker’s  patent  cement,  but  there 
is  a much  superior  article  prepared  from  the  stone  discovered  by  William  Atkin- 
son, Esq.,  on  the  estate  of  the  Earl  of  Mulgrave,  known  by  the  name  of  Atkinson’s 
cement.  At  the  first,  it  costs  a little  more  than  the  Roman  cement,  but  it  w'ill 
bear  a great  deal  more  sand  than  the  former,  is  of  a more  delicate  stone  color, 
and  for  situations  constantl}^  exposed  to  the  action  of  water  it  is  not  surpassed  by 
any  cement  now’  in  existence. 

Roman  Cement  is  prepared  from  the  kind  of  stone  called  clay-balls,  or  septaria, 
by  being,  after  the  manner  of  manufacturing  plaster,  first  broken  into  pieces  of  a 
convenient  size,  slowly  calcined  in  kilns  or  ovens,  and  afterwards  ground  to  a 
fine  pow’der,  and  put  into  proper  casks.  Two  parts  of  composition,  wdth  three 
parts  of  clean  grit  sand,  will  form  a very  durable  substitute  for  stone.  In  select- 
ing the  sand,  great  care  must  be  taken  to  procure  it  possessing  qualities  of  a sharp 
and  binding  nature,  free  from  clay  or  mud.  If  it  cannot  be  had  free  from  these, 
it  must  be  washed  pei’fectly  clean  in  fresh  water. 

After  the  walls  intended  to  be  covered  have  been  w’ell  soaked  with  water,  the 
cement  must  be  prepared  by  the  haw'k-boy  on  a board  made  for  the  purpose,  add- 
ing as  much  water  as  brings  it  to  the  consistency  of  paste.  No  more  must  be 
mixed  than  can  be  used  in  ten  minutes.  It  must  be  laid  on  with  the  greatest  ex- 
pedition, in  a coat  of  three  fourths  of  an  inch  thick.  After  being  well  floated  by 
means  of  the  floating-rule,  the  hand-float  must  be  incessantly  used  to  bring  it  to 
a firm  and  solid  surface  before  it  sets,  wdfich  takes  place  within  fifteen  minutes  if 
the  cement  be  good. 

After  the  w’ork  has  been  drawn  and  jointed  to  imitate  w’ell-bonded  masonry,  it 
may  be  colored  wdth  a wash  composed  of  five  ounces  of  copperas  to  every  gallon 
of  water,  mixed  w’ith  a sufficient  quantity  of  fresh  lime  and  cement,  adding  the 
colors  necessary  to  produce  an  exact  imitation  of  any  particular  stone  which  may 


78 


PRACTICAL  MASONRY. 


be  required.  When  this  mode  of  coloring  is  executed  with  judgment,  and  finish- 
ed with  taste,  so  as  to  produce  a picturesque  effect,  by  touching  the  divisions 
with  rich  tints  of  ochre,  umber,  &c.,  it  is  with  difficulty  distinguished  from  real 
stone.  It  has  been  attempted,  and  in  some  cases  very  successfully,  to  produce 
ancient  Gothic  ruins  in  cement,  and  although,  to  consummate  the  deception,  great 
skill  and  judgment  are  required,  yet  we  have  no  doubt  that,  by  paying  proper 
attention  to  the  style  of  architecture,  as  well  as  the  manner  of  coloring,  imitations 
of  tliis  kind  might  be  carried  to  great  perfection. 

Terra  Cotta  is  an  excellent  as  well  as  durable  composition,  made  use  of  at 
the  present  day  very  advantageously  for  all  kinds  of  exterior  decorations.  It  is  a 
composition  of  pipe-clay,  stone  bottles,  glass,  and  flint,  well  pounded  together, 
and  sifted  through  a very  fine  sieve,  a small  portion  of  silver  sand  being  afterwards 
added.  The  above  ingredients  must  first  be  well  mixed  in  a dry  state,  and  then 
water  added  to  reduce  them  to  the  pliability  of  moulder’s  clay.  The  mixture  thus 
formed,  having  remained  in  this  state  for  two  or  three  days,  must  be  beat  or  tem- 
pered in  a similar  manner  to  moulding  clay,  after  which  it  is  fit  for  use. 

When  applied  to  capitals,  the  bell  or  cover  must  be  prepared  not  more  than 
two  and  a half  inches  thick,  the  stuff  of  which  it  is  composed  being  of  a coarser 
nature  than  that  used  for  its  embellishments.  After  the  ornaments,  as  the  leaves, 
volutes,  &.C.,  have  been  modelled,  they  must  be  moulded  in  plaster,  and  squeezes 
of  artificial  stone  taken  from  the  moulds,  well  cleaned  up  with  appropriate  tools, 
and  fixed  to  the  bell.  It  is  necessary,  when  the  ornaments  are  fitted,  to  bore  two 
or  three  holes,  three  fourths  of  an  inch  in  diameter,  on  those  parts  of  the  bell  where 
the  enrichments  are  to  be  placed,  in  order  to  let  the  damp  air  escape  in  the  process 
of  burning. 

To  fix  the  ornaments,  procure  some  of  the  dry  composition,  and  let  it  remain  in 
water  about  one  day,  then  take  out  the  portion  that  remains  at  the  bottom,  which, 
being  well  chafed  on  a hawk,  composes  the  stuff  for  fixing. 

After  the  bell  and  the  back  of  the  enrichments  have  been  well  wrought,  a little 
soft  stuff  is  rubbed  on  each,  and  the  ornaments  attached  to  the  bell  in  the  usual 
way. 

The  capital  being  then  in  a fit  state  for  drying,  must  be  left  in  the  open  air  for 
that  purpose,  and,  when  thoroughly  dried,  placed  in  the  kiln,  which  is  composed  of 
the  same  materials  as  a common  oven,  but  of  a somewhat  different  construction, 
as  the  flue  must  extend  entirely  over  the  covered  ceiling  of  the  kiln,  and  be  per- 
fectly clear  of  the  ornament. 

In  the  burning  of  terra  cotta,  it  is  necessary  to  commence  with  a very  slow 
fire,  gradually  increasing  it  for  the  first  week,  after  which  a brisk  fire  must  be 
kept  up  for  three  days  and  nights  without  intermission.  The  front  of  the  kiln 


OF  EXTERNAL  COMPOSITIONS. 


79 


must  then  be  closed  with  an  iron  plate,  to  prevent  the  ingress  of  the  atmospheric 
air.  Having  remained  three  days  in  this  situation,  it  is  considered  sufficiently 
burnt,  and  the  kiln  must  be  gradually  opened,  as  the  sudden  admission  of  the  air 
will  cause  the  ornaments  to  crack  or  splinter. 

Method  of  moulding  Terra  Cotta.  The  models  being  executed  in  clay, 
as  is  usual  in  moulding  plaster  ornaments,  they  must  be  moulded  in  the  same 
manner  as  figures  and  busts,  with  this  difference,  that  the  clay  must  not  be 
oiled,  nor  the  joints  of  the  plaster-pieces  which  compose  the  mould.  Instead 
of  oiling  the  model,  it  is  washed  with  pure  water,  when  the  moulder  may 
commence  his  operations.  The  various  joints  of  the  plaster-pieces  in  the 
mould  must  be  touched  with  a small  brush  containing  a little  liquid  clay 
(instead  of  oil,  which  is  the  general  method),  and  great  care  taken  in  the  forma- 
tion of  the  different  joints,  as  the  pieces  cannot  be  taken  from  the  model 
to  be  cut  and  fitted,  but  must  all  be  brought  to  their  proper  shapes  while 
they  remain  on  it.  When  the  sufficient  number  of  pieces  are  made,  so  as  to 
completely  envelope  the  model,  a case  of  plaster  must  be  put  over  the  whole.  In 
taking  the  form  of  the  model,  it  is  requisite  to  soak  the  whole  in  water,  in  order 
that  they  may  leave  the  more  readily,  which  being  done,  the  mould  must  be  well 
washed  and  put  into  the  case  and  gradually  dried  in  the  air,  when  it  will  be  fit 
for  use  without  the  process  of  seasoning  in  oil,  as  is  customary  in  casting  in 
plaster  from  a plaster  mould.  . 

Manner  of  procuring  Impressions  from  the  Mould  in  Terra  Cotta  (sometimes  i 
called  Squeezing).  The  mould  being  dry,  the  workman  must  take  a little  of 
the  finer  stuff  in  his  hands,  and  press  a thin  coat  over  the  whole  of  the  face  of  the 
mould,  adding  on  the  back  that  of  a coarse  quality,  rubbing  in  small  portions  at  a 
time,  so  that  the  ornament  may  be  firm  and  solid.  Immediately  after  squeez- 
ing, the  ornament  must  be  taken  from  the  mould,  cleaned  up,  and  fixed  in  its 
place.  When  the  mould  has  been  used  two  or  three  times,  it  is  liable  to  become 
damp,  which  prevents  the  impressions  from  leaving  expeditiously  ; in  this  case, 
for  the  purpose  of  destroying  its  adherence,  sprinkle  a little  fine  flint-dust  into  the 
mould.  These  methods  of  moulding  and  casting  may  be  applied  not  only  to 
capitals,  but  also  to  all  kinds  of  work  in  this  composition,  such  as  coats  of  arms, 
vasCs,  foundations,  figures,  and  busts,  always  taking  the  precaution  never  to 
allow  the  substance  of  artificial  stone  to  exceed  tw^o  inches  and  one  half.  For 
any  greater  thickness  will  be  liable  to  injure  in  burning. 

Mastic  is  intended  for  an  external  composition,  possessing  peculiar  properties, 
which  in  some  cases  render  it  superior  to  Roman  cement,  having  the  power  of 
resisting  heat  and  frost,  adhering  to  iron,  copper,  and  even  glass,  with  equal 
tenacity. 


80 


PRACTICAL  MASONRY. 


It  is  generally  applied  to  the  exteriors  of  mansions,  but  it  may  also  be  very 
beneficially  used  for  laying  the  floors  of  halls,  kitchens,  &,c. 

Mastic  is  composed  of  pounded  stone,  silver  sand,  litharge,  and  red-lead, 
and  when  manufactured  has  the  appearance  of  very  fine  sand.  It  will  be  perceiv- 
ed the  manner  of  working  mastic  is  entirely  different  from  that  of  Roman  cement. 

To  one  hundred-w^eight  of  mastic  add  one  gallon  of  linseed  oil,  and  let  them 
be  well  incorporated,  which  must  be  effected  by  treading  them  together  with 
the  feet  until  the  amalgamation  is  complete,  and  must  be  continued  until  all  the 
bright  spots  disappear ; it  will  then  be  fit  for  use. 

The  Manner  of  using  Mastic.  The  joints  of  the  brick-work  being  well 
cleaned  out,  the  work  must  be  correctly  plumbed  up  by  means  of  flat-headed 
nails,  and  screeds  for  the  guidance  of  the  floating-rule  formed  with  Roman  cement, 
and  kept  about  one  inch  in  breadth.  This  being  done,  the  bricks  must  be  well 
saturated  with  boiled  linseed  oil  of  the  best  quality,  and  the  mastic  laid  on  with 
the  hand  and  laying-trowel.  The  floating-rule  is  then  passed  carefully  over  the 
work,  and  when  the  space  between  the  screeds  is  sufficiently  filled  up.  it  must  be 
floated  with  a hand-float  until  it  assumes  the  appearance  of  highly  polished 
stone,  the  screeds  then  cut  out,  their  places  filled  with  mastic,  and  properly  trow- 
elled into  the  rest  of  the  work. 

These  directions  will  be  proper  for  large  works,  but  where  windows  and 
doors  occur,  it  will  be  necessary  to  attach  strips  of  wood  on  to  the  reveals 
to  project  the  thickness  of  the  intended  mastic-work,  and  when  the  preparations 
for  forming  the  reveals  by  shifting  the  strip  of  wood  to  the  outside  of  the  plaster- 
ing, projecting  as  before  to  guide  the  hickness  of  the  reveals.  When  well  trow- 
elled the  strips  are  taken  off  and  nail-holes  filled,  and  angles  well  cleaned  down. 
Thus  this  process  is  completed. 

To  run  Mastic  Mouldings.  In  order  to  run  mouldings  with  mastic,  a mould 
of  wood  must  be  cut,  in  every  way  three  eighths  of  an  inch  less  than  the  intended 
moulding,  the  ground  or  inner  part  of  the  moulding  being  formed  of  pieces  of 
broken  bricks  or  tiles,  and  with  the  wooden  mould  run  out  with  Roman  cement 
and  afterwards  with  mastic,  the  mastic  mould  being  cut  to  the  full  size,  the 
edges  mounted  with  brass,  iron,  or  copper.  All  ornaments  executed  in  mastic 
must  be  cast  in  plaster-moulds  similar  to  those  used  in  figure-casting,  with- 
out being  seasoned  in  oil,  but  used  in  their  dry  state,  and  kept  well  pol- 
ished with  a linen  cloth.  All  heavy  ornaments  for  soffits  and  entablatures 
should  be  cut  through  the  plastering  to  the  brick-w'ork  in  a dovetail  form  some- 
thing less  than  the  figure,  and  as  many  nails  as  convenient  driven  in  the  back 
of  the  figure,  and  the  hole  filled  with  Roman  cement  in  a soft  state,  then  the 
figure  properly  adjusted  in  its  intended  place.  All  small  enrichments  may  be 
set  with  white-lead. 


OF  EXTERNAL  COMPOSITIONS, 


81 


Mastic  Floors.  The  groundwork  being  completely  dry,  and  the  bricks 
properly  cleaned  and  saturated  with  boiled  linseed  oil,  the  screeds  formed  with 
Roman  cement,  for  the  purpose  of  floating  or  levelling,  the  mastic  mortar  between 
the  screeds  being  about  one  half  of  an  inch  thick,  then  cut  out  the  screeds  and 
fill  their  places  with  mastic,  and  trowel  it  down  level  with  the  other  work. 

Bailey’s  Composition.  This  composition  is  a valuable  invention,  of  recent 
date,  and  may  be  used  with  great  advantage,  without  being  injured  by  the  action 
of  frost,  on  the  exterior  of  public  or  private  buildings.  This  is  composed  of  un- 
slacked lime  well  ground  to  a fine  powder,  and  kept  in  air-tight  casks  until  used. 
It  is  prepared  by  adding  one  third  of  sharp  and  clean  river-sand.  Reduce  it  by 
clean  water  in  the  manner  of  preparing  Roman  cement. 


11 


82 


PEACTICAL  MASONEY. 


CHAPTER  III. 

PRACTICAL  GEOMETRY,  ADAPTED  TO  MASONRY  AND  STONE-CUTTING. 

SECTION  L — On  the  Position  of  Lines  and  Points. 

As  the  construction  of  every  complex  object  in  nature  consists  of  certain 
combinations  of  the  simple  operations  of  geometry,  and  as  positions  cannot  be 
understood  without  angles  and  parallel  lines,  it  will  be  necessary  to  treat  of  the 
practical  part  of  this  science,  at  least  as  far  as  the  operations  of  the  positions 
of  lines  and  points  are  concerned,  in  order  to  render  the  construction  and  the 
language  of  geometry  familiar  to  the  student  in  their  applications  to  the  princi- 
ples of  masonry. 


PROBLEM  I. 

From  a given  point  in  a given  straight  line  to  draw  a perpendicular. 

Plate  I.  Let  AB,^g-.  1,  be  a given  straight  line,  and  c the  given  point.  In 
AB  take  two  equal  distances,  cd  and  c e.  From  d,  as  a centre,  with  any  radius 
greater  than  cd  or  c e,  describe  an  arc  at  f,  and  with  the  same  radius,  from  the 
point  e,  describe  another  arc  intersecting  the  former  at  /,  and  draw  /c,  and  /c  is 
the  perpendicular  required. 

PROBLEM  II. 

From  the  one  extremity  of  a straight  line  to  draw  a perpendicular. 

Fig.  2.  Let  AB  be  the  given  straight  line,  and  let  it  be  required  to  draw  a 
perpendicular  from  the  extremity  B.  On  one  side  of  the  line  A B take  any  con- 
venient point  c ; and  from  c,  as  a centre,  with  any  radius  that  will  cut  the  line, 
describe  an  arc  d B c,  intersecting  A B in  the  point  d ; through  c draw  the  di- 
ameter d e,  and  join  e B,  and  e B is  the  perpendicular  required. 

PROBLEM  III. 

From  a given  point  out  of  a straight  line  to  let  fall  a perpendicular. 

Fig.  3.  Let  A B be  the  given  straight  line,  and  c the  given  point ; it  is  re- 
quired to  draw  a straight  line  from  c,  perpendicular  to  A B.  From  c,  as  a centre, 
with  any  distance  that  will  cut  the  line  A B,  describe  an  arc  intersecting  A B in 
the  points  d and  e ; from  d,  as  a centre,  with  any  radius  greater  than  the  half  of 


/V.  1. 


,L  1 ."i  il-*  ( } I :v  T S \ X .!<)  1^  1.  K .S  . 


n « Sr. 


ON  THE  POSITION  OF  LINES  AND  POINTS. 


I 


83 


de,  describe  an  arc,  and  from  e,  with  the  same  radius,  describe  another  arc  inter- 
secting the  former  in  f,  and  draw  / c,  and  fc  is  the  perpendicular  required. 

The  criterion  of  the  truth  of  the  method  of  Jig.  2 is  that  of  the  angle  in  a 
semicircle  being  a right  angle. 


PROBLEM  IV. 

At  a given  point  in  a given  straight  line,  to  make  an  angle  equal  to  a given 
angle. 

Fig.  4.  Let  C B A be  the  given  angle,  and  E F the  given  straight  line.  Let 
it  be  required  to  draw  a straight  line,  at  the  point  E,  to  make  an  angle  with  the 
line  E F,  equal  to  the  angle  C B A.  From  the  point  B,  with  any  radius,  describe 
an  arc  meeting  BA  in  A,  and  B C in  g- ; and  from  the  point  E,  with  the  same 
radius,  describe  an  arc  ik,  meeting  E F in  i.  IMake  ik  equal  to  gh,  and  through 
k draw  the  straight  line  E D,  and  F E D is  the  angle  required. 

PROBLEM  V. 

Through  a given  point  f to  draw  a straight  line  parallel  to  a given  straight 
line  A B. 

Fig.  5.  Let  /be  the  given  point,  and  AB  the  given  straight  line.  Draw  any 
straight  line /e,  meeting  A B in  c,  and  draw  g/t,  making  the  angle  A^B  equal  to 
/cB.  Make  gk  equal  to  e/.  Through  the  points / and  A draw  the  line  C D, 
and  C D is  parallel  to  A B,  as  required. 

PROBLEM  VI. 

To  draw  a straight  line  parallel  to  a given  straight  line  at  a given  distance 
from  the  given  straight  line. 

Fig.  6.  Let  A B be  the  given  straight  line  ; it  is  required  to  draw  a straight 
line  at  a given  distance  from  B C.  In  A B take  any  two  points  e and  f ; from  e, 
with  the  given  distance,  describe  an  arc  g A ; and  from  / with  the  same  distance, 
describe  another  arc  ik.  Draw  the  line  C D to  touch  the  arcs  gh  and  ik,  and 
C D is  parallel  to  A B,  as  required. 

PROBLEM  VII. 

To  bisect  a given  straight  line  A B by  a perpendicular. 

Fig.  7.  From  the  point  A,  as  a centre,  with  any  radius  greater  than  the  half 
of  AB,  describe  an  arc  cd;  and  from  B,  with  the  same  radius,  describe  another 
arc  intersecting  the  former  at  c and  d,  and  draw  c d,  intersecting  A B in  e ; then 
A B is  divided  in  e,  as  required.  • 


84 


PRACTICAL  MASONRY. 


PROBLEM  VIII, 

Upon  a given  straight  line  to  describe  an  equilateral  triangle. 

Fig.  8.  Let  A B be  the  given  straight  line.  From  the  point  A,  with  the  ra- 
dius A B,  describe  an  arc,  and  from  the  point  B,  with  the  radius  B A,  describe 
another  arc,  intersecting  the  former  in  C,  and  draw  the  straight  lines  C A and 
C B , then  A B C is  the  equilateral  triangle  required. 

PROBLEM  IX. 

Upon  a given  straight  line  to  describe  a triangle,  of  which  the  sides  shall  be 
equal  to  three  given  straight  lines,  provided  that  any  one  of  the  three  given 
lines  be  less  than  the  sum  of  the  other  two. 

Fig.  9.  Let  the  three  given  straight  lines  be  A,  B,  C,  and  let  D F be  the 
straight  line  on  which  the  triangle  is  required  to  be  described.  Make  D F equal 
to  the  given  straight  line  A.  From  D,  with  the  radius  of  the  line  B,  describe 
an  arc,  and  from  F,  with  the  radius  of  the  line  C,  describe  another  arc,  meet- 
ing the  arc  described  from  D in  the  point  E.  Draw  E D and  E F,  then  DE  F 
is  the  triangle  required. 


PROBLE.M  X. 

Given  the  base  and  height  of  the  segment  of  a circle,  to  find  the  centre  of 
the  circle,  and  thence  to  describe  the  arc. 

Fig.  10.  Let  A C be  the  base ; bisect  A C in  D by  the  perpendicular  B E ; 
make  D B equal  to  the  height,  and  join  the  points  A and  B.  Make  the  angle 
B A E equal  to  A B E,  and  the  point  E is  the  centre  required. 

From  the  point  E,  with  the  radius  E A or  E B,  describe  the  arc  AB  C ; then 
A B C is  the  arc  required. 

N.  B.  The  centre  must  also  have  been  found  by  bisecting  AB  by  a perpen- 
dicular, which  would  have  met  B E in  the  point  E. 

PROBLEM  XL 

Given  two  converging  lines,  through  a given  point  in  one  of  them  to  draw  a 
third  straight  line,  so  that  the  angles  on  the  same  side  of  the  line  thus  drawn,  made 
by  this  line  and  each  of  the  first  two  given  lines,  may  be  equal  to  each  other. 

Fig.  13.  Let  the  two  converging  lines  be  A C and  B D,  and  let  A be  the 
given  point.  Draw  A E parallel  to  B D ; bisect  the  angle  CAE  by  the  straight 
line  A B ; then  will  the  angles  CAB  and  D B A be  equal  to  one  another. 

For,  suppose  A E .to  be  produced  from  A to  F,  and  suppose  A C and  B D to 
be  produced  to  meet  in  some  point  G,  then  A C would  have  been  a line  falling  upon 


ON  THE  POSITION  OF  LINES  AND  POINTS. 


85 


the  two  parallel  straight  lines  A F and  B D,  and  consequently  making  the  angle 
at  G equal  to  the  angle  FAC;  and  since  the  three  angles  of  every  triangle  are 
equal  to  two  right  angles,  and  since  the  angles  F AC,  CAB,  BA  E,  are  also  equal 
to  two  right  angles,  and  since  F A C is  equal  to  the  vertical  angle  of  the  triangle, 
the  angle  C A E is  equal  to  the  sum  of  the  angles  at  the  base  ; and  therefore, 
since  C A B is  half  the  sum,  the  angle  A B D must  be  equal  to  the  other  half. 

PROBLEM  XII. 

Given  two  converging  lines,  to  describe  the  arc  of  a circle  through  a given 
point  in  one  of  them,  without  having  recourse  to  a centre,  so  that  the  point  of 
convergency  may  be  in  the  centre  of  the  arc. 

Fig.  14.  Let  AB  and  E F be  the  two  converging  lines,  and  A the  given  point 
through  which  the  arc  is  to  pass.  Draw  AE,  making  the  angles  BAE  and  FEA 
equal  to  each  other.  Bisect  A E by  the  perpendicular  C D,  and  draw  A h mak- 
ing the  angles  BAA  and  DAA  equal  to  one  another  ; then  A A is  the  chord  of  the 
arc,  and  nA  is  the  versed  sine.  Suppose  now  that  the  three  points  A,  A,  E,  are 
transferred  to  A,  B,  C,fig.  15.  Join  B A and  B C.  Produce  B A to  c?,  and  B C 
to  e.  Make  the  edge  of  a slip  of  wood  to  the  angle  d B e.  Move  the  edge  d^e 
of  the  slip  of  wood  so  that  the  point  B may  be  upon  A ; then  move  this  slip 
again,  so  that  while  the  part  B d of  the  edge  of  the  slip  is  sliding  upon  the  pin 
at  A,  and  the  part  B e upon  the  pin  at  C,  a pencil  held  to  the  angle  B will  de- 
scribe a curve ; then  this  curve  will  be  the  arc  required. 

PROBLEM  XIII. 

Given  two  straight  lines,  to  find  a third  proportional. 

Fig.  1 1.  From  any  point  A,  draw  any  two  straight  lines  B A,  A C,  at  any  an- 
gle. Make  A B equal  to  one  of  the  given  straight  lines,  and  A C equal  to  the 
other ; and  in  A B make  A d equal  to  A C.  Join  B C and  draw  d e parallel  to 
B C,  meeting  A C in  e ,*  then  A e is  the  third  proportional  required. 

^ Or,  if  A e be  equal  to  one  of  the  given  straight  lines,  and  A d equal  to  the 
other.  Make  A C equal  to  A d.  Join  d e and  draw  C B parallel  to  ed  ; then  A B 
is  the  third  proportional. 


, PROBLEM  XIV. 

Given  a straight  line,  and  how  divided,  to  divide  another  in  the  same  propor- 
tion. 

Fig.  12.  Draw  the  lines  B A,  A C,  as  in  the  preceding  problem,  and  let  A B be 
the  given  divided  line,  d and  e being  the  points  of  division,  and  let  A C be  the 
line  to  be  divided.  Join  B C and  draw  eg  and  df  parallel  to  B C,  meeting  A C 


86 


PRACTICAL  MASONRY. 


in  /and  g ; then  A C is  divided  in  f and  g,  in  the  same  proportion  as  A B is  di- 
vided in  the  points  d and  e. 


PROBLEM  XV. 

Given  three  straight  lines,  to  find  a fourth  proportional. 

Fig.  12.  The  angle  BAG  being  made  as  before,  let  Ae  be  equal  to  one  of 
the  given  lines,  A d equal  to  a second,  and  A f equal  to  the  third.  Join  d f and 
draw  eg  parallel  to  df;  then  A^  is  the  fourth  proportional. 


SECTION  II.  — On  the  Species,  Nature,  and  Construction  of  Curve  Lines. 

The  geometrial  orders  of  lines  employed  in  architecture,  in  the  construction 
of  arches,  are  circular  and  elliptic,  and  occasionally  parabolic,  hyperbolic,  cycloid- 
al, and  catenarian  curves. 

In  houses,  the  chief  lines  employed  in  the  construction  of  arches  and  vaults 
are  circular  and  elliptic  curves,  generally  a semi,  and  sometimes  less,  but  seldom 
or  never  greater.  When  a circular  or  elliptic  arc  is  adopted,  one  of  the  axes  of 
the  curve  is  most  frequently  situated  upon  the  springing  line ; but  is  sometimes 
placed  so  as  to  be  parallel  to  it.  The  most  usual  portions  of  circular  or  elliptic 
curves  are  the  semi ; and  in  the  pointed  style  of  architecture,  parabolic  and  hy- 
perbolic curves  are  very  frequently  employed. 

In  bridge  building,  besides  circular  and  elliptic  curves,  which  are  the  most 
often  used  in  the  construction  of  stone  arches,  cycloidal  curves  may  also  be  in- 
troduced. In  chain  bridges,  or  bridges  of  suspension,  not  only  the  circular  and 
parabolic  curves,  but  that  of  the  catenarian  may  be  employed.  The  suspending 
chains  necessarily  assume  the  form  of  catenarian  curves  ; but  the  road-way  may 
be  any  curve  line  whatever ; but  as  all  curves  are  nearly  circular  at  the  vertex, 
it  will  be  better  to  employ  those  in  the  construction  of  works  which  are  suscepti- 
ble of  the  most  easy  calculation. 

Among  the  numerous  orders  of  curve  lines,  the  parabolic  affords  the  most 
easy  means  of  computing  its  ordinates  and  tangents,  which  will  be  found  neces- 
sary in  ascertaining  the  rise  and  inclination  of  the  road-way  in  all  points  of  the 
curve,  from  either  extreme  to  the  centre  of  the  bridge. 

The  base  of  an  arc  is  that  upon  which  the  arc  is  supposed  to  stand ; and  the 
highest  point  of  an  arc  is  that  in  which  a straight  line  parallel  to  the  base  would 
meet  the  curve,  without  the  possibility  of  coming  within  the  area  included  by 
the  curve  and  its  base,  and  this  point  is  called  the  summit  of  the  arc. 

As  the  curves  employed  in  building  are  generally  symmetrical,  therefore  they 


'Hi  hUl  Ji]  D R A 'LS 


PI  2. 


iv.n:ir7/j*/777  fir. 


I-  ■ 

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4 Pa 


OF  CURVED  LINES. 


87 


are  equal  and  similar  on  each  side  of  the  summit,  and  their  areas  are  equal  and 
similar  on  each  side  of  the  perpendicular  from  the  middle  of  the  base. 

PROBLEM  I. 

To  describe  a semi-ellipse  upon  the  transverse  axis. 

Plate  II.  Let  A a,  Jig.  12,  be  the  axis  major,  and  let  B C,  bisecting  A a per- 
pendicularly in  the  point  C,  be  the  semi-conjugate  axis. 

Upon  the  straight  edge  m i of  a rule,  mark  the  point  7n  at  or  near  one  of  its 
ends,  and  the  point  / at  a distance  from  m equal  to  B C,  the  semi-conjugate 
axis,  and  the  point  k at  a distance  from  m equal  to  AC  or  C a,  the  semi- 
transverse  axis  ; the  distance  k I being  equal  to  the  difference  of  the  two  axes. 
To  find  any  point  in  the  curve,  place  the  point  k in  the  line  B C produced,  and 
the  point  / in  the  axis  A a ; and  mark  the  paper  or  plane  on  which  the  figure  is 
to  be  described  at  the  point  m.  Proceed  in  this  manner  until  a sufficient  num- 
ber of  points  are  found,  and  draw  a curve  through  them,  and  the  curve  will  be 
the  semi-ellipse  required. 


PROBLEM  II. 

Upon  a given  double  ordinate,  to  describe  the  segment  of  an  ellipse  to  a 
given  abscissa,  and  to  a given  semi-axis  in  that  abscissa. 

Figs.  13  and  14.  Let  M m be  the  double  ordinate,  P H the  abscissa,  and  H C 
the  semi-axis. 

Through  the  centre  C,  draw  KA'  parallel  to  IVlwi.  From  either  extremity  m of 
the  double  ordinate  as  a centre,  with  the  distance  H C of  the  given  semi-axis  as 
radius,  describe  an  arc  intersecting  K k in  r.  Draw  ?n  r intersecting  H C in  or 
produce  mr  and  H C to  meet  in  q ; then  m q,Jig.  13,  will  be  the  semi-transverse, 
and  mr  the  semi-conjugate,  and  in  Jig.  14,  the  contrary  will  take  place;  mr  will 
be  the  semi-transverse,  and  m q the  semi-conjugate ; the  two  axes  being  thus 
found,  the  curve  may  be  described  as  in  the  immediately  preceding  problem. 

PROBLEM  III. 

Given  two  conjugate  diameters,  to  find  any  number  of  points  in  the  curve, 
and  thence  to  describe  it. 

Figs.  15  and  16.  Let  A a,  BZ»,  be  the  conjugate  diameters.  Draw  AD 
parallel  to  B C,  and  B D parallel  to  C A.  Divide  A D and  A C each  into  the 
same  number  of  equal  parts.  Through  the  points  of  division  in  A C draw 
straight  lines  from  b,  and  through  the  points  of  division  in  AD,  draw  other 
straight  lines  to  the  point  B,  meeting  those  drawn  from  b in  the  points  /,  g,  h. 


88 


PRACTICAL  MASONRY. 


Draw  a curve  line  through  the  points  A,  f,  g,  h,  B,  which  will  be  one  quarter  of 
the  whole  figure.  The  other  three  will  of  course  be  found  in  the  same  manner. 

PROBLEM  IV. 

To  draw  a normal,  or  line  perpendicular  to  the  curve  of  an  ellipse  at  a given 
point  in  the  curve. 

Fig.  17.  Let  the  curve  be  A B «,  and  let  A a be  the  transverse  axis,  and 
C B the  semi-conjugate,  and  let  it  be  required  to  draw  a line  from  the  point  71 
perpendicular  to  the  curve.  With  A C the  semi-axis  major  as  a radius,  from 
the  point  B describe  an  arc,  intersecting  A a in  the  foci  . From  the  points 
and  through  the  point  n,  draw/'^/  and /e,  and  bisect  the  angle  end,  and 
the  bisecting  line  11  N will  be  perpendicular  to  the  curve  as  required. 

PROBLEM  V. 

To  draw  a tangent  to  the  curve  of  an  ellipse  at  a given  point. 

Fig.  17.  Let  m be  the  given  point.  Draw  fm,  and  produce  fm  io  g,  and 
join  the  points  /',  m.  Bisect  the  angle  f'mg,  and  the  bisecting  line  T t will 
be  the  tangent  required. 


PROBLEM  VI. 

The  curve  of  an  ellipse  being  given,  to  find  the  two  axes. 

Fig.  18.  Let  AMN^im  be  the  given  curve  within  the  figure;  draw  any 
two  parallel  lines  Mm,  N;i.  Bisect  Mm  in  0,  and  N in  p,  and  draw  the 
straight  line  A op  a.  Bisect  Aa  in  C,  from  C as  a centre,  with  any  radius  that 
will  cut  the  curve  ; describe  the  arc  rr',  intersecting  the  curve  in  the  points  rr\ 
and  draw  the  straight  line  rr'.  Bisect  r r' in /i,  and  through  the  points  A and 
C draw  the  line  de,  then  de  is  the  axis  major;  and  a line  drawn  through  the 
point  C at  right  angles  to  d e,  to  meet  the  curve  on  each  side  of  C,  will  be  the 
axis  minor. 


PROBLEM  VII. 

With  a given  abscissa  and  ordinate,  to  describe  a parabola." 

Fig.  19.  Let  AB  be  the  abscissa,  and  B C the  ordinate.  Draw  CD  paral- 
lel to  B A,  and  A D parallel  to  B C.  Divide  C D and  C B each  into  the  same 
number  of  equal  parts.  From  the  points  1,  2,  3,  in  C D,  draw  lines  to  A,  and 
from  the  points  1,  2,  3,  in  C B,  draw  lines  parallel  to  BA,  meeting  the  former 
lines  to  A in  the  points  /,  g,  h.  Draw  the  curve  C fg  h A,  which  will  be  one 
half  of  the  parabola ; the  other  half  will  be  found  in  the  same  manner.  The 
radius  of  curvature  at  the  point  A is  half  the  parameter. 


OF  LINES  AND  PLANES. 


89 


PROBLEM  VIII. 

The  curve  of  a parabola  being  given,  to  find  the  parameter. 

Fig.  19.  Let  C AN  be  the  curve  of  the  parabola.  Bisect  B C in  the  point 
2,  and  draw  A 2 and  2 d perpendicular  to  A 2,  meeting  A B produced  in  d ; then 
B d is  one  fourth  part  of  the  parameter. 

For  A B : B 2 : : B 2 : B d;  now  let  A B = «,  B C = 6,  then  B 2 = ; hence 

a : j b ::  Y h : i p;  whence  ap  = F ot  p — 


PROBLEM  IX. 

To  draw  a tangent  to  any  point  M,  in  the  curve  of  a parabola. 

Fig.  1 9.  Draw  the  ordinate  P M,  and  produce  P A to  Make  A q equal 
to  A P,  and  draw  the  straight  line  q IM  ; then  q M will  be  the  tangent  required. 
For  the  subtangent  of  the  curve  is  double  to  the  abscissa. 


PROBLEM  X. 


To  form  the  curve  of  a parabola  by  means  of  tangents. 

Fig.  20.  Let  A C be  the  double  ordinate.  Draw  D B bisecting  A C,  and 
make  D B equal  to  the  abscissa.  Produce  D B to  E,  and  make  B E equal  to 
B D.  Draw  the  two  straight  lines  E A and  E C.  Divide  A E and  E C each  in 
the  same  proportion,  or  into  the  same  number  of  equal  parts,  at  the  points  1,  2,  3|^ 
&,c.,  in  each  line.  Draw  the  straight  lines  1-1,  2-2,  3-3,  &c.,  and  their  intersec-'^ 
tions  will  circumscribe  the  curve  of  the  parabola  as  required. 

Scholium.  Small  portions  of  the  curves  of  conic  sections,  near  to  the  vertices, 
may  be  described  with  compasses  so  as  not  to  be  perceptible  ; and  thus,  not 
only  in  the  parabola,  but  in  the  ellipse ; and  in  the  hyperbola,  the  radius  of  curva- 
ture at  the  vertices  is  half  the  parameter,  which  passes  through  the  focus.  In 
the  parabola,  the  parameter  is  a third  proportional  to  the  abscissa  and  ordinate ; 
and  in  the  ellipse  and  hyperbola,  the  parameter  is  a third  proportional  to  the 
transverse  and  conjugate  axis  ; and  therefore  may  be  easily  found  by  lines  or  by 
calculation  on  large  works,  such  as  bridges,  &.c. 


SECTION  III. — Of  the  Position  of  Lines  and  Planes,  and  the  Properties  arisino 

FROM  their  Intersections. 

A PLANE  is  a surface  in  w^hich  a straight  line  may  coincide  in  all  directions. 

A straight  line  is  in  a plane,  when  it  has  two  points  in  common  with  that 
plane. 


12 


90 


PRACTICAL  MASONRY. 


Two  straight  lines  which  cut  each  other  in  space,  or  would  intersect  if  pro- 
duced, are  in  the  same  plane ; and  two  lines  that  are  parallel  are  also  in  the 
same  plane. 

Three  points  given  in  space,  and  not  in  a straight  line,  are  necessary  and 
sufficient  for  determining  the  position  of  a plane.  Hence  two  planes,  which  have 
three  points  common,  coincide  with  each  other. 

The  intersection  of  two  planes  is  a straight  line. 

Plate  I.  When  two  planes  AB  C D,  A B E F,  jig.  16,  intersect,  they  form 
between  them  a certain  angle,  which  is  called  the  inclination  of  the  two  planes, 
and  which  is  measured  by  the  angle  contained  by  two  lines  ; one  drawn  in  each 
of  the  planes  perpendicular  to  their  line  of  common  section. 

Thus,  if  the  line  A F,  in  the  plane  A B E F,  be  perpendicular  to  A B,  and  the 
line  A D,  in  the  plane  A B C D,  be  perpendicular  also  to  A B,  then  the  angle 
FAD  is  the  measure  of  the  inclination  of  the  planes  A B E F,  A B C D. 
When  the  angle  FAD  is  a right  angle,  the  two  planes  are  perpendicular. 

Fig.  1 7.  A line  A B is  perpendicular  to  a plane  P Q,  when  the  line  A B is 
perpendicular  to  any  line  B C,  in  the  plane  P Q,  which  passes  through  the  point 
B,  where  the  line  meets  the  plane.  The  point  B is  called  the  foot  of  the  per- 
pendicular. 

A line  A ^,fig.  18,  is  parallel  to  a plane  P Q,  when  the  line  A B is  parallel  to 
another  straight  line  C D,  in  the  plane  P Q. 

If  a straight  line  have  one  of  its  intermediate  points  in  common  with  a plane, 
the  whole  line  will  be  in  the  plane. 

Two  planes  are  parallel  to  one  another  when  they  cannot  intersect  in  any 
direction. 

The  intersections  of  two  parallel  planes  with  a third  are  parallel.  Thus,  in  jig. 
19,  the  lines  A B,  C D,  comprehended  by  the  parallel  plane  P Q,  RS,  are  par- 
allel. 

Any  number  of  parallel  lines  comprised  between  two  parallel  planes  are  all 
equal.  Thus  the  parallel  lines  A a,  B 6,  C c,  . . . .,  fig.  20,  comprised  by  the 
parallel  planes  P Q,  R S,  are  all  equal. 

If  two  planes  C D E F,  G II I fig.  21,  are  perpendicular  to  a third  plane  P Q, 
their  intersection  A B will  be  perpendicular  to  the  third  plane  P Q. 

If  two  straight  lines  be  cut  by  several  parallel  planes,  these  straight  lines  will 
be  divided  in  the  same  proportion. 


N 


PI  J. 


:ii  !l  1 1:1  'i‘  8 K K 'I  W S iD)  J'*  AiRV  III  K 3. 


W7  S'c. 


OF  THE  RIGHT  SECTIONS  OF  ARCHES. 


91 


SECTION  IV.  — Of  the  Right  Sections  of  Arches  or  Vaults. 

PROBLEM  I. 

To  describe  the  arc  of  a circle  which  shall  have  a given  tangent  at  a given 
point,  and  which  shall  touch  another  given  arc. 

Plate  III.  Let  B k,fig.  4,  be  one  of  the  given  arcs,  and  lau  the  other,  and  let 
it  be  required  to  describe  the  arc  of  a circle,  which  shall  touch  the  arc  B k in 
the  point  k,  and  the  arc  lau  in  some  point  to  be  found;  let  g be  the  centre  of 
the  arc  B k. 

Draw  g A',  and  make  kp  equal  to  the  radius  of  the  circle  lau.  Draw  a straight 
line  from  p to  q,  the  centre  of  the  arc  lau,  and  bisect  pq  by  a perpendicular, 
meeting  kg  in  m.  Join  the  points  m,  q,  and  prolong  mq  to  /.  It  is  manifest  that 
mk  and  ml  are  equal ; therefore,  from  m,  with  the  radius  mk  or  ml,  describe  an 
arc  kl;  and  kl  will  be  the  arc  required. 

PROBLEM  II. 

To  describe  an  oval,  representing  an  ellipse,  to  any  given  dimensions  of  length 
and  breadth,  given  in  position. 

Let  A «,  B h,fig.  1,  be  the  two  given  lines  bisecting  each  other  in  C ; A « being 
equal  to  the  length,  and  B 6 to  the  breadth. 

Find  a third  proportional  to  this  semi-axis  C «,  C B,*  and  make  a h equal  to  the 
third  proportional ; also  find  a third  proportional  to  C B,  C «,  f and  make  Bg-  equal 
to  the  third  proportional. 

Make  the  angle  B^A  equal  to  about  L5^,  and  let  gk  meet  A a in  the  point  i. 
From  g,  with  the  radius  g B,  describe  an  arc  B k,  and  from  h,  with  the  radius  h a, 
describe  an  arc  I a.  Describe  the  arc  kl  by  the  preceding  problem  to  touch  the 
arc  B k in  A,  and  to  touch  the  arc  a Z at  /,  and  thus  one  quarter  of  the  oval  will  be 
completed  ; the  other  three  will  be  found  by  placing  the  centres  in  their  proper 
positions. 

Three  or  more  points  a,  h,  c,  might  easily  have  been  found  in  the  curve. 
Thus,  draw  A d parallel  to  B b,  and  B d parallel  to  C A.  Divide  A d into  four 
equal  parts,  and  divide  A C also  into  four  equal  parts  at  1,2,  3.  From  b and 
through  1,  2,  3,  in  C A,  draw  b a,  bb,  be,  and  from  the  points  1,  2,  3,  in  A d,  draw 
towards  B,  to  intersect  the  former  in  a,  b,  c,  so  that  we  may  find  the  radius  of 

* Thus,  in  Jig.  2,  draw  the  two  lines  G A,  A H.  making  an  angle  with  each  other  ; make  a c equal  to  a C, 
Jig.  1,  and  A d equal  to  C H,Jig.  2 ; and  make  A e equal  to  A d.  Join  cd,  and  draw  ef  parallel  to  cd ; then 
af  is  the  third  proportional. 

f That  is,  in  Jig.  2,  make  A c equal  A G or  a C,  Jig.  1,  and  A d equal  to  C B or  C i.  Jig.  1,  and  make  A G 
equal  to  Ac,  and  join  cd.  Draw  G H parallel  to  d c;  then  A H is  the  third  proportional. 


92 


PRACTICAL  MASONRY. 


curvature  upon  the  sides,  and  at  the  two  ends,  by  finding  the  centre  of  a cir- 
cle passing  through  three  points  at  each  extremity,  the  extremity  being  the  mid- 
dle point. 

Fig.  3 exhibits  the  use  of  this  method  of  describing  an  oval,  in  finding  the 
direction  of  the  joints  of  arches  so  as  to  agree  with  the  normals  drawn  from  the 
several  divisions  of  the  inner  arc.  The  arcs  are  marked  the  same  as  in  fig.  2. 

REMARK, 

When  the  height  of  the  arch  is  equal  to  or  greater  than  half  the  span,  and 
when  it  is  not  necessary  that  the  vertical  angle  should  be  given,  the  curves  of 
the  intrados  and  extrados  on  the  one  side  may  be  described  from  the  same  cen- 
tre, as  also  those  of  the  other  side  from  another  centre. 

The  most  easy  Gothic  arch  to  describe  is  that  of  which  the  height  of  the  in- 
trados is  such  as  to  be  the  perpendicular  of  an  equilateral  triangle,  described  up- 
on the  sparing  line  as  a base,  and  these  centres  are  the  points  to  which  the  ra- 
diating joints  must  tend. 

Gothic  arches  seldom  exceed  in  height  the  perpendicular  of  the  equilateral  tri- 
angle inscribed  in  the  intrados  of  the  aperture  ; but  when  the  arch  is  surmounted 
and  the  height  less  than  the  perpendicular  of  the  equilateral  triangle  made  upon 
the  base,  draw  a straight  line  from  one  extremity  of  the  base  to  the  vertex,  and 
bisect  this  line  by  a perpendicular.  From  the  point  where  the  perpendicular 
meets  the  base  of  the  arch,  and  with  a radius  equal  to  the  distance  between  this 
point  and  the  extremity  of  the  base  joined  to  the  vertex,  describe  an  arc  between 
the  two  points,  joined  by  the  straight  line,  and  the  curve  which  forms  one  side  of 
the  intrados  will  be  complete.  In  the  same  manner  will  be  found  the  curve  on 
the  other  side,  (see  fig.  5,)  so  that  by  only  two  centres  the  whole  of  the  intrados 
will  be  formed. 

The  curves  of  all  kinds  of  Gothic  arches  whatever  may  be  described  by 
means  of  conic  parabola,  to  a given  vertical  angle,  and  to  any  given  dimensions. 
Thus,  in  fg.  7,  let  C e,  Cf,  be  the  two  tangents,  and  A c,  and  B /,  the  heights  of 
their  extremities.  Divide  A c and  e C each  into  the  same  number  of  equal  parts 
by  the  points  1,  2,  3,  in  each  of  these  lines.  Draw^  lines  from  the  corresponding 
points  1-1,  2-2,  3-3,  &.c. ; and  the  intersections  will  form  the  curve  of  one  side 
of  the  intrados,  as  we  have  already  seen.  The  curve  on  the  other  side  w'ill  be 
formed  in  the  same  manner. 

Join  B C,  and  bisect  it  in  g,  and  join  gf,  intersecting  the  curve  in  /.  Draw  h k 
^parallel  to  C B,  meeting  g/  in  k.  Make  / i equal  to  I k,  and  i h joined  is  a tan- 
gent at  h.  Hence,  h m perpendicular  to  h i is  the  joint. 


ON  TE  E HEDEALS. 


93 


CHAPTER  IV. 


SECTION  I.  — On  the  Nature  and  Construction  of  Trehedrals. 

DEFINITIONS. 

Every  stone  bounded  by  six  quadrilateral  planes  or  faces  forms  a solid,  of 
which  the  surfaces  terminate  on  eight  points,  every  three  surfaces  in  one  point. 
Every  three  planes  thus  terminating  is  termed  a solid  angle  or  trehedral. 

The  angles  formed  by  the  intersections  of  the  faces  with  one  another,  or  the 
three  plane  angles,  are  called  sides  of  the  trehedral,  and  the  angles  of  inclination 
are  called,  by  way  of  distinction  from  the  other,  simply  angles. 

The  three  sides,  as  well  as  the  three  angles,  are  each  called  a part ; so  that 
the  whole  trehedral  consists  of  six  parts;  and  if  any  three  of  these  parts  be  given, 
the  remaining  three  can  be  found. 

Therefore,  in  bodies  constructed  of  stone,  which  are  intended  to  have  their 
solid  angles  to  consist  of  three  plane  angles,  the  construction  of  such  bodies  may 
be  reduced  to  the  consideration  of  the  trehedral. 

As  to  the  remaining  surface  of  the  solid  which  incloses  the  solid,  completely 
making  a fourth  side  to  the  trehedral,  it  may  be  of  any  form  whatever,  regular  or 
irregular,  or  consisting  of  many  surfaces  ; it  or  they  have  nothing  to  do  in  the 
construction. 

The  parts  of  the  trehedral,  which  may  be  obtained  from  three  given  parts, 
are  the  very  same  as  three  parts  found  in  a spherical  triangle  from  three  given 
parts.  This  is,  in  fact,  the  same  as  spherical  trigonometry. 

We  shall  not,  however,  enter  into  any  operose  analytical  investigations,  but 
treat  the  subject  in  the  most  simple  manner,  according  to  the  rules  of  solid 
geometry  ; and  only  those  trehedrals,  which  have  two  of  their  planes  at  a right 
angle  with  each  other  (though  there  are  many  cases  in  which  the  oblique  trehe- 
dral would  be  necessary)  ; as  the  bounds  prescribed  for  this  work  will  not  admit 
of  such  an  extension  of  the  principles. 

If  the  trehedral  have  two  of  its  planes  perpendicular  to  each  other,  it  is  called 

right-angled  trehedral ; each  of  the  two  faces  thus  forming  a right  angle  is 
called  a leg,  and  the  remaining  side,  joining  each  leg,  is  called  the  hypothenuse. 

PROBLEM  I. 

Given  two  legs  of  a right-angled  trehedral,  to  find  the  hypothenuse. 


94 


PRACTICAL  MASONRY. 


Plate  II.,  figs.  1,  2,  3,  and  4.  Let  PON  and  P O R be  the  given  legs.  Draw 
P R perpendicular  to  O P,  and  PQ  perpendicular  to  ON.  From  O,  as  a centre, 
with  the  radius  O R,  describe  an  arc  intersecting  P Q in  Q,  and  join  O Q,  and 
Q O N is  the  hypothenuse  required. 

Demonstration.  — Suppose  the  triangle  P 0 R revolved  upon  0 P,  until  P R 
become  perpendicular  to  the  plane  of  the  triangle  O P N,  then  the  plane  of  the 
triangle  OPR  will  be  perpendicular  to  the  plane  of  the  triangle  O P N. 

Again,  suppose  the  triangle  O N Q to  revolve  upon  O N,  and  let  P Q,  or  P Q 
produced,  intersect  O N in  w,  then  m Q will  always  be  in  a plane  passing  through 
P m and  the  plane  described  by  m Q will  be  perpendicular  to  the  plane  m O P ; 
and  as  P R is,  by  supposition,  also  perpendicular  to  the  plane  m O P,  therefore 
P R and  m Q being  thus  situated  in  the  same  plane  will  meet,  except  they  are 
parallel. 

Let  mQ  therefore  be  revolved  until  the  straight  line  mQ  fall  upOn  the  point  R; 
let  Q then  be  supposed  to  coincide  with  R,  then  because  Q,  by  supposition, 
coincides  with  R,  and  the  point  O is  common  to  the  straight  lines  O Q and  O R, 
therefore  the  straight  lines  O Q and  O R having  two  common  points  will  coincide, 
and  therefore  m O Q will  be  the  hypothenuse  required. 

PROULEiM  II. 

Given  the  hypothenuse  and  one  of  the  legs,  to  find  the  other  leg. 

Figs.  1,  2,  3,  and  4.  Let  N O Q be  the  given  hypothenuse,  and  NOP  the  given 
leg,  and  let  these  two  parts  be  attached  to  each  other  by  the  straight  line  O N. 

In  O N take  any  point  m,  and  through  m draw  P Q perpendicular  to  O N. 
Draw  PR  perpendicular  to  O P.  From  the  point  O,  with  the  radius  O Q,  de- 
scribe an  arc  Q R and  join  O R ; then  will  P O R be  the  other  leg,  as  required. 

These  four  diagrams  show  the  various  positions  in  which  the  data  may  be 
placed  ; every  one  will  frequently  occur  in  practice. 

PROBLEM  III. 

Given  the  two  legs  of  a right-angled  trehedral,  to  find  one  of  the  angles  at  the 
hypothenuse. 

Figs.  5 and  6.  Let  the  two  given  legs  be  P O N and  P O R.  In  O P take  any 
point  P,  and  draw  P N perpendicular  to  O N,  and  P R perpendicular  to  P O,  and 
P K parallel  to  O N.  Make  P K equal  to  P R,  and  join  N K ; then  P NK  will 
be  the  angle  at  the  hypothenuse. 

In  fig.  5,  the  two  legs  lie  upon  separate  parts  ; and  in  fig.  6,  one  of  the  legs 
lies  upon  the  other. 

Fig.  7 exhibits  the  same  principle  applied  in  finding  a series  of  bevels  or 


ON  TREHEDRALS. 


95 


angles  made  by  the  hypothenuse  and  a leg.  Thus  let  the  two  legs  be  P O N 
and  POR.  From  any  point  m,  in  OP,  draw'  wR  perpendicular  to  OP.  On 
O /«,  as  a diameter,  describe  the  semicircle  O q m,  intersecting  O N in  5',  and  join 
q m.  Make  mr  equal  to  mq,  and  join  ?’R;  then  PrR  will  be  the  angle  re- 
quired. 


PROBLEM  IV. 

Given  one  of  the  legs  and  the  inclination  of  the  hypothenuse  to  that  leg,  to  find 
the  other  leg. 

Figs.  8 and  9.  Let  N O P be  the  given  leg.  In  O N take  any  point  m,  and 
draw  m i perpendicular  to  O N.  Make  i m p equal  to  the  angle  which  the  leg 
NOP  makes  with  the  hypothenuse.  Through  any  point  i,  in  7«  i,  draw  P p 
parallel  to  O N,  and  P Q,  perpendicular  to  O P.  IMake  P Q equal  to  ip,  and  join 
O Q,  and  Q O P will  be  the  other  leg. 

PROBLE.M  V. 

Given  one  of  the  legs  and  the  angle  which  the  hypothenuse  forms  with  that 
leg,  to  find  the  hypothenuse. 

Figs.  10  and  11.  In  N O,  take  any  point  ???,  and  draw  7n?i  perpendicular 
to  ON.  Make  nmp  equal  to  the  angle  which  the  hypothenuse  makes  with  the 
leg  N O P.  From  the  point  m as  a centre,  with  any  radius  mn,  describe  an  arc 
n p.  Draw  p P,  n Q parallel  to  N O,  and  P Q perpendicular  to  N O,  and  join 
O Q ; then  N O Q is  the  hypothenuse  required. 

GENERAL  APPLICATIONS  OF  THE  TREIIEDRAL  TO  TANGENT  PLANES. 

Example  I.  — Given  the  inclination  and  seat  of  the  axis  of  an  oblique  cylinder 
or  cylindroid,  to  find  the  angle  which  a tangent  makes  at  any  point  in  the  circum- 
ference of  the  base  with  the  plane  of  the  base. 

Plate  III.,  figs.  6 and  9.  Let  AEB  O be  the  base  of  the  cylinder  or  cylin- 
droid, C B the  seat  of  the  axis,  and  let  B C D be  the  angle  of  inclination,  and  let 
O be  the  point  where  the  tangent  plane  touches  the  curved  surface  of  the  solid. 

Draw  O N,  a tangent  line,  at  the  point  O in  the  base,  and  draw  O P parallel 
to  C B.  IMake  the  angle  P O R equal  to  BCD,  and  draw  P R perpendicular 
to  P O. 

Then,  if  the  triangle  P O R be  conceived  to  be  revolved  round  the  line  P O as 
an  axis,  until  its  plane  become  perpendicular  to  the  plane  of  the  circle  A E B C, 
the  straight  line  O R will,  in  this  position,  coincide  with  the  cylindrical  surface, 
and  a plane  touching  the  cylinder  or  cylindroid  at  O will  pass  through  the*  lines 
O N and  O R.  Here  wall  now  be  given  the  two  legs  POR  and  P O N of  a right- 


96 


PRACTICAL  MASONRY. 


angled  trehedral  to  find  the  angle  which  the  hypothenuse  makes  with  the  base. 
Draw  P Q perpendicular  to  O N,  intersecting  it  in  w,  and  draw^  P S perpendicu- 
lar to  P Q.  Make  P S equal  to  P R,  and  join  m S ; then  P m S is  the  angle  re- 
quired. 

The  hypothenuse  will  be  easily  constructed  at  the  same  time,  thus : — make 
m Q equal  to  m S,  and  join  O Q,  then  N O Q will  be  the  hypothenuse  required. 

In  fig.  1,  the  method  of  finding  the  angle  which  the  tangent  plane  makes  with 
the  base  and  the  hypothenuse  is  exhibited  at  four  different  points.  In  the  two  first 
points  O from  A in  the  first  quadrant,  the  tangent  planes  make  an  acute  angle  at 
each  point  O ; but  in  the  second  quadi’ant,  they  make  an  obtuse  angle  at  each 
point  O. 

Fig.  8 is  the  second  position  of  the  construction  from  the  point  A,  for  finding 
the  angle  which  the  tangent  plane  makes  with  the  base,  and  for  finding  the 
hypothenuse  enlarged  ; in  order  to  show  a more  convenient  method  by  not  only 
requiring  less  space,  but  less  labor.  It  may  be  thus  described,  the  two  given 
legs  being  P'  O'  R'  and  P'  O'  N'. 

Draw  P' m perpendicular  to  O'  N',  meeting  O N in  m.  In  P'  O',  make  P'  v' 
equal  to  V m,  and  draw  the  straight  line  v R',  then  V v R'  will  be  the  inclination 
of  the  tangent  plane  at  the  point  O. 

Again,  in  O' P' make  O'/'  equal  to  O' m\  and  draw  /'w'  parallel  to  P' R'. 
From  O',  with  the  radius  O'  R',  describe  an  arc  meeting  /'  u in  m',  and  draw  the 
straight  line  O'  u ; then  /'  O'  u is  the  hypothenuse. 

For  since  P'S'  is  equal  to  P' R',  and  P'f'  equal  to  P' m',  and  the  angles 
m'P'  S'  and  v'  P'  R'  are  right  angles  ; therefore  the  triangle  v P'  R'  is  equal  to  the 
triangle  m P'  S',  and  the  remaining  angles  of  the  one  equal  to  the  remaining  an- 
gles of  the  other,  each  to  each ; hence  the  angle  P'  v R'  is  equal  to  the  angle 
P' m'  S'. 

Again,  because  O'  /'  is  equal  to  O'  m',  and  O'Q'  is  equal  to  O'  R',  and  O'  u is 
also  equal  to  O'  R' ; therefore  O' w'  is  equal  to  O'Q',  and  since  the  angles  O'  /'  u 
and  0'r?i'Q'  are  each  a right  angle,  therefore  the  two  right-angled  triangles  have 
their  hypothenuses  equal  to  each  other,  and  have  also  one  leg  in  each,  equal  to 
each  other ; therefore  the  remaining  side  of  the  one  triangle  is  equal  to  the  re- 
maining side  of  the  other,  and  therefore  also  the  angles  which  are  opposite  to  the 
equal  sides  are  equal ; hence  the  angle  P'  O'  u is  equal  to  N'  O'  Q'. 

By  considering  this  construction  by  the  transposition  of  the  triangles,  the  whole 
of  the  angles  wdiich  the  tangent  planes  make  at  a series  of  points  O in  figs.  6 
and  9,  and  their  hypothenuses,  may  be  all  found  in  one  diagram,  as  fig.  4. 

Thus,  in^g.  10,  if  the  angles  A C O,  A C O',  A C O",  A C O'",  be  respectively 
equal  to  A C O,  A C O,'  A C O,"  A C O'",  fig.  6,  and  in  fig.  1 0,  the  semicircle 


ON  THE  PROJECTION  OF  A STRAIGHT  LINE,  &c.  97 

A O'  B be  described,  and  if  C D be  drawn  perpendicular  to  A B,  and  the  angles 
CAD,  C B D,  be  made  equal  to  B C 6 ; then  each  half  of  Jig.  10  being 

constructed  as  in  jig.  8,  the  angles  at  m,  m',  m",  w'",  will  be  respectively  equal 
to  the  angle  P m S,  P' m S',  Q"  m"  S",  Q"  m'"  S",  in  Jig.  6. 

Also,  in  Jig.  1 0,  the  angles  CAE,  C A g,  C A A,  C B i,  C B A:,  C B F,  will  be 
the  hypothenuses  at  the  point  A,  O,  O',  O",  O'",  B,  in  Jig.  6. 

We  may  here  observe,  6,  that  the  angles  which  the  tangent  planes  make 
with  the  plane  of  the  base  in  the  first  quadrant  are  acute ; and  those  in  the  sec- 
ond quadrant  are  obtuse,  and  are  the  supplements  of  the  angles  P m S ; and, 
moreover,  that  all  the  angles  which  constitute  the  hypothenuses  of  the  trehedral 
are  acute,  whether  in  the  first  quadrant  or  second  quadrant*  of  the  semicircle 
A OB. 


SECTION  II,  — On  the  Projection  of  a Straight  Line  bent  upon  a Cylindric  Surface, 
AND  THE  Method  of  Drawing  a Tangent  to  such  a Projection. 

PROBLEM  I. 

Given  the  development  of  the  surface  of  the  semi-cylinder,  and  a straight  line 
in  that  development,  to  find  the  projection  of  the  straight  line  on  a plane  passing 
through  the  axis  of  the  cylinder,  supposing  the  development  to  encase  the  semi- 
cylindric  surface. 

Fig.  1 1 . Let  A B C be  the  development  of  the  cylindric  surface,  B C being 
the  development  of  the  semi-circumference,  and  let  A C be  the  straight  line 
given. 

Produce  C B to  D,  making  B D equal  to  the  diameter  of  the  cylinder.  On  B D, 
as  a diameter,  describe  the  semicircle  BED,  and  divide  the  semicircular  arc 
BED  into  any  number  of  equal  parts,  at  1,2,  3,  &c. ; and  its  development  B C 
into  the  same  number  of  equal  parts,  at  the  points./,  g,  h,  &c.  Draw  the  straight 
lines  fk,  gl,hm,  See.,  parallel  to  B A,  meeting  A C at  the  points  k,  /,  m,  &c.;  also, 
parallel  to  B A,  draw  the  straight  lines  I 0,  2 p,  3 g,  &c.,  and  draw  k 0,  lp,mq,  &lc., 
parallel  to  C D ; and  the  points  0,  p,  q,  &,c.,  are  the  projections  or  seats  of  the 
points  k,  /,  m,  &c.,  in  the  development  of  the  straight  line  A C. 

The  projection  of  a screw  is  found  by  this  method  : — B D may  be  considered 
as  the  diameter  of  the  cylinder  from  which  the  screw  is  formed ; and  the  angle 
BAG  the  inclination  of  the  thread  with  a straight  line  on  the  surface ; or  B C A 
the  inclination  of  the  thread  with  the  end  of  the  cylinder.  The  same  principle 
also  applies  to  the  delineations  of  the  hand-rails  of  stairs,  and  in  the  construction 
of  bevel  bridges. 


13 


98 


PRACTICAL  MASONRY. 


PROBLEM  II. 

Given  the  entire  projection  of  a helix  or  screw,  in  the  surface  of  a semi-cylinder, 
and  the  projection  of  a circle  in  that  surface  perpendicular  to  the  axis,  upon  the 
plane  passing  through  the  axis  to  draw  a tangent  to  the  curve  at  a given  point. 

Fig.  12.  Let  B P K be  the  projection  of  the  helix  or  screw,  and  B A the 
projection  of  the  circumference  of  a circle,  and  since  this  circle  is  in  a plane  per- 
pendicular to  the  plane  of  projection,  it  will  be  projected  into  a straight  line  A B, 
equal  to  the  diameter  of  the  cylinder. 

On  A B as  a diameter,  describe  the  semicircle  A r B,  and  draw  P r perpendic- 
ular to  and  intersecting  AB  in  9,  join  the  points  e,  r,  and  produce  er  to /. 

Produce  A B to  C,  so  that  B C may  be  equal  to  the  semicircular  arc  B r A. 
Draw  C D perpendicular  to  B C,  and  make  C D equal  to  A K,  and  draw  the 
straight  line  B D ; then  B D will  be  the  development  of  the  curve  line  B P K. 

Draw  P u parallel  to  A C,  meeting  B D in  ii,  and  draw  ii  t perpendicular  to 
B C.  Draw  r g perpendicular  to  er,  and  make  rg  equal  to  B t.  Draw^n  per- 
pendicular to  A C,  meeting  B C in  n,  and  draw  the  straight  line  n P ; then  nP 
will  touch  the  curve  at  the  point  P. 

Or  the  tangent  may  be  drawn  independent  of  B C D thus:  — Draw  P r per- 
pendicular to  AB,  and  rg  a tangent  at  r.  Make  equal  to  ihe  development  of 
r B,  and  draw  g n perpendicular  to  B C,  meeting  B C in  n,  and  join  n P,  which  is 
the  tangent  required. 


SECTION  III.  — Application  of  Geometry  to  Planes  and  Elevations,  and  also  to  the 

Construction  of  Arches  and  Vaults. 

PRELIMINARY  PRINCIPLES  OF  PROJECTION. 

If  from  a point  A',  Plate  \\.,fig.  1,  in  space,  a perpendicular  K'a  be  let  fall  to 
any  plane  P Q whatever,  the  foot  a of  this  perpendicular  is  called  the  projection 
of  the  point  A'  upon  the  plane  P Q. 

If  through  different  points  A',  B',  C',  D', jigs.  2,  3,  4,  of  any  line 

A'  B'  C'  D' whatever  in  space,  perpendiculars  A'a,  B'6,  C'c,  D'd, be 

let  fall  upon  any  plane  P Q whatever,  and  if  through  a,  h,  c,  d, the  pro- 
jection of  the  points  A',  B',  C',  D', in  the  plane  P Q,  a line  be  drawn, 

the  line  thus  drawn  will  be  the  projection  of  the  line  A'  B'  C'  D' given 

in  space. 

If  the  line  A'B'  C'  D' fig.  3,  be  straight,  the  projection  abed will 

also  be  a straight  line  ; and  if  the  line  B'  C'  D' Jig.  2,  be  a curve  not  in 

a plane  perpendicular  to  the  plane  P Q,  the  curve  abed which  is  the  pro- 


. utr/i/rt  s f'f 


WW.WiLson  Sr 


APPLICATION  OF  GEOMETRY  TO  PLANES,  &c. 


99 


jection  of  the  curve  A'  B'  C'  D' in  space,  will  be  of  the  same  species  with 

the  original  curve,  of  which  it  is  the  projection.  Hence,  in  this  case,  if  the 
original  curve  A'B'C'D'  . . . . be  an  ellipse,  a parabola,  a hyperbola,  &c.,  the 
projection  abed  ...  . will  be  an  ellipse,  a parabola,  a hyperbola,  &c.  The  cir- 
cle and  the  ellipse  being  of  the  same  species,  the  projected  curve  may  be  a 
circle  or  ellipse,  whether  the  original  be  a circle  or  ellipse,  as  in  fig.  4. 

The  plane  in  which  the  projection  of  any  point,  line,  or  plane  figure  is  situa- 
ted, is  called  the  plane  of  projection,  and  the  point  or  line  to  be  projected  is 
called  the  primitive. 

The  projection  of  a curve  will  be  a straight  line  when  the  curve  to  be  project- 
ed is  in  a plane  perpendicular  to  the  plane  of  projection.  Hence  the  projection  of 
a plane  curve  is  a straight  line. 

If  a curve  be  situated  in  a plane  which  is  parallel  to  the  plane  of  projection,  the 
projection  of  the  curve  will  be  another  curve  equal  and  similar  to  the  curve  of 
which  it  is  the  projection. 

The  projection  upon  a plane  of  any  curve  of  double  curvature  whatever  is  al- 
ways a curve  line. 

In  order  to  fix  the  position  and  form  of  any  line  whatever  in  space,  the  position 
of  the  line  is  given  to  each  of  two  planes  which  are  perpendicular  to  each  other; 
the  one  is  called  the  horizontal  plane  and  the  other  the  vertical  plane  ; the  pro- 
jection of  the  line  in  question  is  made  on  each  of  these  two  planes,  and  the  two 
projections  are  called  the  two  projections  of  the  line  to  be  projected. 

Thus  we  see,  in  fig.  5,  where  the  parallelogram  U V W X represents  the  hori- 
zontal plane,  and  the  parallelogram  U V Y Z represents  the  vertical  plane,  the 
projection  a 6 of  the  line  A'B'  in  space  upon  the  horizontal  plane  U V W X is 
called  the  horizontal  projection,  and  the  projection  A B of  the  same  line  upon  the 
vertical  plane  U V Y Z is  called  the  vertical  projection. 

The  two  planes  upon  which  we  project  any  line  whatever  are  called  the 
planes  of  projection. 

The  intersection  U V of  the  two  planes  of  projection  is  called  the  ground- 
line. 

When  we  have  two  projections  ab,  A B,  of  any  line  A'  B'  in  space,  the  line 
A'B' will  be  determined  by  erecting  to  the  planes  of  projection  the  perpendiculars 
a A',  B i'.  . . .,  A A',  B B'.  . . . through  the  projections  a,b,  ....;  A,  B, . . . . 
of  the  original  points  A',  B',  ....  of  the  line  in  question.  For  the  perpendiculars 
a A',  A A,  erected  from  the  projections  a,  A,  of  the  same  point  A',  will  intersect 
each  other  in  space  in  a point  A',  which  will  be  one  of  these  in  the  line  in 
question.  It  is  clear  that  the  other  points  must  be  found  in  the  same  manner  as 
this  which  has  now  been  done. 


100 


PRACTICAL  MASONRY. 


When  we  have  obtained  the  two  projections  of  a line  in  space,  whether  imme- 
diately from  the  line  itself,  or  by  any  other  means  whatever,  we  must  abandon 
this  line  in  order  to  consider  its  two  projections  only.  Since,  when  we  design  a 
working  drawing,  we  operate  only  upon  the  two  projections  of  this  line  that  we 
have  brought  together  upon  one  plane,  and  we  no  longer  see  any  thing  in  space. 

However,  to  conceive  that  w^hich  we  design,  it  is  absolutely  necessary  to  carry 
by  thought  the  operations  into  space  from  their  projections.  This  is  the  most 
difficult  part  that  a beginner  has  to  surmount,  particularly  when  he  has  to  consid- 
er at  the  same  time  a great  number  of  lines  in  various  positions  in  space. 

The  perpendicular  A'  a,  fig.  5,  let  fall  from  any  point  A whatever  in  space  up- 
on the  plane  X V of  projection,  is  called  the  projectant  of  the  point  A'  upon  this 
plane.  Moreover,  the  perpendicular  distance  between  the  point  A'  and  the  hori- 
zontal plane  X V is  called  the  projectant  upon  the  horizontal  plane,  or  simply  the 
horizontal  projectant;  and  the  peipendicular  distance  A' A between  the  original 
point  A'  and  the  vertical  plane  U Y is  called  the  projectant  upon  the  vertical 
plane,  or  simply  the  vertical  projection. 

We  shall  remark,  so  as  to  prevent  any  mistake,  that  the  horizontal  projectant 
A'a  is  the  peipendicular  let  fall  from  the  original  point  upon  the  horizontal  plane, 
and  that  the  vertical  projectant  is  the  perpendicular  let  fall  from  that  point  upon 
the  vertical  plane.  Hence  the  horizontal  projectant  is  parallel  to  the  vertical 
plane,  and  is  equal  to  the  distance  between  the  original  point  and  the  horizontal 
plane  ; and  the  vertical  projectant  is  parallel  to  the  horizontal  plane,  and  is  equal 
to  the  distance  between  the  original  point  and  the  vertical  plane. 

We  may  remark,  that  if  through  a,  fig.  6,  the  horizontal  projection  of  the  point 
A',  we  draw  a perpendicular  o a to  U V,  the  ground-line,  this  perpendicular  a a 
will  be  equal  to  the  measure  of  the  vertical  projectant  A' A;  consequently  the 
distance  of  the  point  A'  to  the  vertical  plane  is  equal  to  the  distance  betw'een  a, 
its  horizontal  projection,  and  U V,  the  ground-line,  measured  in  a perpendicular  to 
U V.  In  like  manner,  if  through  A,  the  vertical  projection  of  the  point  A',  w'e 
draw  a perpendicular  A a to  U V,  the  ground-line,  this  perpendicular  A a will  be 
equal  to  the  measure  of  the  horizontal  projectant  A a ; consequently,  the  distance 
of  this  point  A'  to  the  horizontal  plane  is  equal  to  the  distance  between  A,  its 
vertical  projection,  and  U V,  the  ground-line,  measured  in  a perpendicular  to  U V. 

To  these  very  important  remarks  w e shall  add  one  which  is  not  less  so.  Two 
perpendiculars,  a a,  fig.  6,  A a,  being  let  fall  from  the  projections  a,  A,  to  the 
same  point  A',  upon  the  ground-line  U V,  will  meet  each  other  in  the  same  point 
a of  the  said  ground -line  U V. 

If  we  now  wished  the  two  projections  of  a point  A',  fig.  6,  or  of  any  line 
A'  B'  whatever,  to  be  upon  one  or  the  same  plane,  it  is  sufficient  to  imagine  the 


APPLICATION  OF  GEOMETRY  TO  PLANES,  &c. 


101 


vertical  plane  U V Y Z to  turn  round  the  ground-line  U V,  in  such  a manner  as 
to  be  the  prolongation  of  the  horizontal  plane  U Y W X ; for  it  is  clear  that  this 
plane  will  carry  with  it  the  vertical  projection  A or  A B of  the  point,  or  of  the 
line  in  question.  Moreover,  we  see,  and  it  is  very  important,  that  the  lines  A a, 
B b,  perpendicular  to  the  ground-line  U Y will  not  cease  to  be  so  in  the  motion 
of  the  plane  U Y YZ;  and,  as  the  corresponding  lines  a a,  bh,  are  also  perpen- 
diculars to  the  ground-line  U Y,  it  follows  that  the  lines  a a',  hb\  will  be  the  re- 
spective prolongation  of  the  lines  a a,  6 b. 

Hence  it  results,  when  we  consider  objects  upon  a single  plane,  that  the  projec- 
tions a,  A,  of  the  point  A'  in  space  are  necessarily  upon  the  same  perpendicular 
A a to  the  ground -line  U Y. 

It  is  necessary  to  call  to  mind,  that  the  distance  A a measures  the  distance  from 
the  point  in  space  to  the  horizontal  plane  (the  point  A being  the  vertical  projec- 
tion of  this  point),  and  that  the  line  a a measures  the  distance  from  the  same 
point  in  space  to  the  vertical  plane. 

It  follows,  that  if  the  point  in  space  be  upon  the  horizontal  plane,  its  distance 
with  regard  to  this  last  named  plane  will  be  zero  or  nothing,  and  the  vertical  A a 
will  be  zero  also.  Moreover,  the  vertical  projection  of  this  point  will  be  upon  the 
ground-line  at  the  foot  a of  the  perpendicular  a a let  fall  upon  the  ground-line 
from  the  horizontal  projection  a of  this  point. 

Again,  if  the  point  in  space  be  upon  the  vertical  plane,  its  distance,  in  respect 
of  this  plane,  will  be  zero,  the  horizontal  a a will  be  zero,  and  the  horizontal 
projection  of  the  point  in  question  will  be  the  foot  a of  the  perpendicular  A a let 
fall  upon  the  ground-line  from  the  vertical  projection  A of  this  point. 

In  general,  we  suppose  that  the  vertical  projection  of  a point  is  above  the 
ground-line,  and  that  the  horizontal  projection  is  below ; but  from  what  has  been 
said,  it  is  evident  that  if  the  point  in  space  be  situated  below  the  horizontal  line, 
its  vertical  projection  will  be  below  the  ground-line ; for  the  distance  from  this 
point  to  the  horizontal  plane  cannot  be  taken  from  the  base  line  to  the  top,  but 
from  the  top  to  the  base  with  respect  to  its  plane. 

So,  if  the  point  in  space  be  situated  behind  the  vertical  plane,  its  horizontal 
projection  will  be  above  the  ground-line,  from  which  we  conclude,  — 

1st.  If  the  point  in  question  be  situated  above  the  horizontal  plane,  and  be- 
fore the  vertical  plane,  its  vertical  projection  will  be  above,  and  its  horizontal  pro- 
jection below,  the  ground -line. 

2d.  If  the  point  be  situated  before  the  vertical  plane,  and  below  the  horizontal 
plane,  the  two  projections  will  be  below  the  ground-line. 

3d.  If  the  point  be  situated  above  the  horizontal  plane,  but  behind  the  vertical 
plane,  the  two  projections  will  be  above  the  ground-line. 


102 


PRACTICAL  MASONRY. 


4th.  Lastly.  If  the  point  be  situated  above  the  horizontal  plane,  and  behind 
the  vertical  plane,  the  vertical  projection  will  be  below,  and  the  horizontal  pro- 
jection above,  the  ground-line. 

The  reciprocals  of  these  propositions  are  also  true. 

If  a line  be  parallel  to  one  of  the  planes  of  projection,  its  projection  upon  the 
other  plane  will  be  parallel  to  the  ground-line.  Thus,  for  example,  if  a line  be 
parallel  to  a horizontal  plane,  its  vertical  projection  will  be  parallel  to  the  ground- 
line ; and  if  it  is  parallel  to  the  vertical  plane,  its  horizontal  projection  will  be  par- 
allel to  the  ground-line. 

Reciprocally,  if  one  of  the  projections  of  a line  be  parallel  to  the  ground-line, 
this  line  will  be  parallel  to  the  plane  of  the  other  projection.  Thus,  for  example, 
if  the  vertical  projection  of  a line  be  parallel  to  the  ground-line,  this  line  will  be 
parallel  to  the  horizontal  plane,  and  vice  versa. 

If  a line  be  at  any  time  parallel  to  the  two  planes  of  projection,  the  two  pro- 
jections of  this  line  will  be  parallel  to  the  ground -line;  and  reciprocally,  if  the 
two  projections  of  a line  be  parallel  to  the  ground-line,  the  line  itself  will  be  at 
the  same  time  parallel  to  the  two  planes  of  projection. 

If  a line  be  perpendicular  to  one  of  the  planes  of  projection,  its  projection 
upon  this  plane  will  only  be  a point,  and  its  projection  upon  the  other  plane  will 
be  perpendicular  to  the  ground-line.  Thus,  for  example,  if  the  line  in  question 
be  perpendicular  to  the  horizontal  plane,  its  horizontal  projection  will  be  only  a 
point,  and  its  vertical  projection  will  be  perpendicular  to  the  ground-line. 

Reciprocally,  if  one  of  the  projections  of  a straight  line  be  a point,  and  the 
projection  of  the  other  perpendicular  to  the  ground-line,  this  line  will  be  perpen- 
dicular to  the  plane  of  projection  upon  which  its  projection  is  a point.  Thus 
the  line  will  be  perpendicular  to  the  horizontal  plane,  if  its  projection  be  the 
given  point  in  the  horizontal  plane. 

If  a line  be  perpendicular  to  the  ground-line,  the  two  projections  will  also 
be  perpendicular  to  this  line.  The  reciprocal  is  not  true  ; that  is  to  say,  that 
the  two  projections  of  a line  may  be  perpendicular  to  the  ground-line,  without 
having  the  same  line  perpendicular  to  the  ground-line. 

If  a line  be  situated  in  one  of  the  planes  of  projection,  its  projection  upon 
the  other  will  be  upon  the  ground-line.  Thus,  if  a line  be  situated  upon  a 
horizontal  plane,  its  vertical  projection  will  be  upon  the  ground-line  ; and  if 
this  line  were  given  upon  the  vertical  plane,  its  horizontal  projection  would  be 
upon  the  ground-line. 

Reciprocally,  if  one  of  the  projections  of  a line  be  upon  the  ground-line,  this 
line  will  be  upon  the  plane  of  the  other  projection.  Thus,  for  example,  if  it 
be  the  vertical  projection  of  the  line  in  question  which  is  upon  the  ground,  this 


:V.PPL  IC  ATIO  N OF  GEOMETRA^  TO  PLANES,  &c.  103 


line  will  be  upon  the  horizontal  plane  ; if,  on  the  contrary,  it  were  upon  the 
horizontal  projection  of  this  line  which  was  upon  the  ground-line,  this  line 
would  be  upon  the  vertical  plane. 

If  a line  be  at  any  time  upon  the  two  planes  of  projection,  the  two  pro- 
jections of  this  line  would  be  upon  the  ground-line,  and  the  line  in  question 
would  coincide  with  this  ground-line.  Reciprocally,  if  the  two  projections  of  a 
line  were  upon  the  ground-line,  the  line  itself  would  be  upon  the  ground-line. 

If  two  lines  in  space  are  parallel,  their  projections  upon  each  plane  of  pro- 
jection are  also  parallel.  Reciprocally,  if  the  projections  of  two  lines  are  par- 
allel on  each  plane  of  projection,  the  two  lines  will  be  parallel  to  one  another  in 
space. 

If  any  two  lines  whatever  in  space  cut  each  other,  the  projections  of  their  point 
of  intersection  will  be  upon  the  same  perpendicular  line  to  the  ground-line,  and 
upon  the  points  of  intersection  of  the  projections  of  these  lines.  Reciprocally,  if 
the  projections  of  any  two  lines  whatever  cut  each  other  in  the  two  planes  of  pro- 
jection, in  such  a manner  that  their  points  of  intersection  are  upon  the  same  per- 
pendicular to  the  ground-line,  these  two  lines  in  question  will  cut  each  other  in 
space. 

The  position  of  a plane  is  determined  in  space,  when  we  know  the  intersec- 
tions  of  this  plane  with  the  planes  of  projection.  ' ^ 

The  intersections  A B,  AC,  of  the  plane  in  question,  with  the  planes  of  pro- 
jection, are  called  the  traces  of  this  plane. 

The  trace  situated  in  the  horizontal  plane  is  called  the  horizontal  trace,  and 
the  trace  situated  in  the  vertical  plane  is  called  the  vertical  trace. 

A very  important  remark  is,  that  the  two  traces  of  a plane  intersect  each  other 
upon  the  ground-line. 

If  a plane  be  parallel  to  one  of  the  planes  of  projection,  this  plane  will  have  only 
one  trace,  which  will  be  parallel  to  the  ground-line,  and  situated  in  the  other 
plane  of  projection.  Reciprocally,  if  a plane  has  a trace  parallel  to  the  ground- 
line, this  plane  will  be  parallel  to  the  plane  of  projection  which  does  not  contain 
this  trace.  Thus  : — 

1st.  If  a plane  be  parallel  to  the  horizontal  plane,  this  plane  will  not  have  a 
horizontal  trace,  and  its  vertical  trace  will  be  parallel  to  the  ground-line.  Like- 
wise, if  a plane  be  parallel  to  the  vertical  plane,  this  plane  will  not  have  a verti- 
cal trace,  and  its  horizontal  trace  will  be  parallel  to  the  ground-line. 

2d.  If  a plane  has  only  one  trace,  and  this  trace  parallel  to  the  ground -line, 
let  it  be  in  the  vertical  plane  ; then  the  plane  will  be  parallel  to  the  horizontal 
plane.  So  if  the  trace  of  the  plane  be  in  the  horizontal  plane,  and  parallel  to  the 
ground-line,  the  plane  will  be  parallel  to  the  vertical  plane. 


104 


PRACTICAL  MASONRY. 


If  one  of  the  traces  of  a plane  be  perpendicular  to  the  ground-line,  and  the  oth- 
er trace  in  any  position  whatever,  this  plane  will  be  perpendicular  to  the  plane  of 
projection  in  which  the  second  trace  is.  Thus,  if  it  be  a horizontal  trace  which  is 
perpendicular  to  the  ground -line,  the  plane  will  be  perpendicular  to  the  vertical 
plane  of  projection ; and  if,  on  the  contrary,  the  vertical  trace  be  that  which  is 
perpendicular  to  the  ground-line,  then  the  plane  will  be  perpendicular  to  the  hor- 
izontal plane. 

Reciprocally,  if  a plane  be  perpendicular  to  one  of  the  planes  of  projection 
without  being  parallel  to  the  other,  its  trace  upon  the  plane  of  projection  to  which 
it  is  perpendicular  will  be  to  any  position  whatever,  and  the  other  trace  will  be 
perpendicular  to  the  ground-line.  Thus,  for  example,  if  the  plane  be  perpendic- 
ular to  the  vertical  plane,  the  vertical  trace  will  be  in  any  position  whatever,  and 
its  horizontal  trace  will  be  perpendicular  to  the  ground-line.  The  reverse  will 
also  be  true,  if  the  plane  be  perpendicular  to  the  horizontal  plane. 

If  a plane  be  perpendicular  to  the  two  planes  of  projection,  its  two  traces  will 
be  perpendicular  to  the  ground-line.  Reciprocally,  if  the  two  traces  of  a plane 
are  in  the  same  straight  line  perpendicular  to  the  ground-line,  this  plane  will  be 
perpendicular  to  both  the  planes  of  projection. 

If  the  two  traces  of  a plane  are  parallel  to  the  ground-line,  this  plane  will  be 
also  parallel  to  the  ground-line.  Reciprocally,  if  a plane  be  parallel  to  the 
ground-line,  its  two  traces  will  be  parallel  to  the  ground-line. 

When  a plane  is  not  parallel  to  either  of  the  planes  of  projection,  and  one  of  its 
traces  is  parallel  to  the  ground-line,  the  other  trace  is  also  necessarily  parallel  to 
the  ground-line. 

If  two  planes  are  parallel,  their  traces  in  each  of  the  planes  of  projection  will 
also  be  parallel.  Reciprocally,  if  on  each  plane  of  projection  the  traces  of  the  two 
planes  are  parallel,  the  planes  will  also  be  parallel. 

If  a line  be  perpendicular  to  a plane,  the  projections  of  this  line  will  be  in  each 
plane  of  projection  perpendicular  to  the  respective  traces  in  this  plane.  Recip- 
rocally, if  the  projections  of  a line  are  respectively  perpendicular  to  the  traces  of 
a plane,  the  line  will  be  perpendicular  to  the  plane. 

If  a line  be  situated  in  a given  plane  by  its  traces,  this  line  can  only  intersect 
the  planes  of  projection  upon  the  traces  of  the  plane  which  contains  it.  More- 
over, the  line  in  question  can  only  meet  the  plane  of  projection  in  its  own  projec- 
tion. Whence  it  follows,  that  the  points  of  meeting  of  the  right  line  and  the 
planes  of  projection  are  respectively  upon  the  intersections  of  this  right  line  and 
the  traces  of  the  plane  which  contains  it. 

If  a right  line,  situated  in  a given  plane  by  its  traces,  is  parallel  to  the  horizon- 
tal plane,  its  horizontal  projection  will  be  parallel  to  the  horizontal  trace  of  the 


DEVELOPMENTS  OF  THE  SURFACES  OF  SOLIDS.  105 

given  plane,  and  its  vertical  projection  will  be  parallel  to  the  ground -line.  Like- 
wise, if  the  right  line  situated  in  a given  plane  by  its  traces  is  parallel  to  the 
vertical  plane,  its  vertical  projection  will  be  parallel  to  the  vertical  line  of  the  plane 
which  contains  it,  and  its  horizontal  projection  will  be  parallel  to  the  ground-line. 

Reciprocally,  if  a line  be  situated  in  a given  plane  by  its  traces,  and,  for 
example,  let  its  horizontal  projection  be  parallel  to  the  horizontal  trace  of  the 
given  plane,  this  line  will  be  parallel  to  the  horizontal  plane,  and  its  vertical 
projection  will  be  parallel  to  the  ground-line.  Likewise,  if  the  vertical  pro- 
jection of  the  line  in  question  be  parallel  to  the  vertical  trace  of  the  given  plane, 
this  line  will  be  parallel  to  the  vertical  plane,  and  its  horizontal  projection  will  be 
parallel  to  the  ground-line. 


SECTION  IV. — Ox  THE  Developments  of  the  Surfaces  of  Solids. 

PROBLEM  I. 

To  find  the  development  of  the  surface  of  a right  semi-cylinder. 

Plate  \Y.,fig.  7.  Let  ACDE  be  the  plane  passing  through  the  axis.  On 
A C,  as  a diameter,  describe  the  semicircular  arc  ABC.  Produce  C A to  F, 
and  make  A F equal  to  the  development  of  the  arc  ABC.  Draw  F G parallel 
to  A E,  and  E G parallel  to  A F ; then  AF  GE  is  the  development  required. 

PROBLE.M  II. 

To  find  the  development  of  that  part  of  a semi-cylinder  contained  between 
two  perpendicular  surfaces. 

Figs.  8,  9,  and  10.  Let  A C D E be  a portion  of  a plane  passing  through  the 
axis  of  the  cylinder,  C D and  A E being  sections  of  the  surface,  and  let  D E and 
G F be  the  insisting  lines  of  the  perpendicular  surface  ; also  let  A C be  perpen- 
dicular to  A E and  C D.  On  A C,  as  a diameter,  describe  the  semicircular  arc 
ABC.  Produce  C A to  H,  and  make  A H equal  to  the  development  of  the 
arc  ABC.  Divide  the  arc  ABC,  and  its  development,  each  into  the  same 
number  of  equal  parts  at  the  points  1,  2,  3. 

Through  the  points  1,  2,  3,  &c.,  in  the  semicircular  arc  and  in  its  develop- 
ment, draw  straight  lines  parallel  to  AE,  and  let  the  parallel  lines  through  1,  2, 
3,  in  the  arc  ABC,  meet  F G in  p,  q,  r,  &.C.,  and  AC  in  A:,  /,  m,  &c.  Trans- 
fer the  distances  kp,  Iq,  mr,  &lc.,  to  the  development  upon  the  lines  1 a,  2 
3 c,  &.C.  Through  the  points  F,  a,  b,  c,  &c.,  draw  the  curve  line  F c I.  In  the 
same  manner  draw  the  curve  line  E K ; then  F E K I will  be  the  development 
required. 


14 


106 


PRACTICAL  MASONRY. 


PROBLEM  III. 

To  find  the  development  of  the  half  surface  of  a right  cone,  terminated  by  a 
plane  passing  through  the  axis. 

Fig.  1 1 . Let  ACE  be  the  section  of  the  cone  passing  along  the  axis 
A E ; and  C E the  straight  lines  which  terminate  the  conic  surface,  or  the  two 
lines  which  are  common  to  the  section  CAE  and  the  conic  surface ; and  let 
A C be  the  line  of  common  section  of  the  axal  plane,  and  the  base  of  the  cone.  * 

On  A C,  as  a diameter,  describe  a semicircle  ABC.  From  E,  with  the 
radius  E A,  describe  the  arc  A F,  and  make  the  arc  A F equal  to  the  semi- 
circular arc  ABC,  and  join  E F ; then  the  sector  A E F is  the  development 
of  the  portion  of  the  conic  surface  required. 

• 

PROBLEM  IV. 

To  find  the  development  of  that  portion  of  a conic  surface  contained  by  a 
plane  passing  along  the  axis,  and  two  surfaces  perpendicular  to  that  plane. 

Fig.  12.  Let  ACE  be  the  section  of  the  cone  along  the  axis,  and  let  AC 
and  GI  be  the  insisting  lines  of  the  perpendicular  surfaces.  Find  the  develop- 
ment A E F as  in  the  preceding  problem.  Divide  the  semicircular  arc  ABC, 
and  the  sectorial  arc  A F,  each  into  the  same  number  of  equal  parts,  at  the 
points  1,  2,  3,  &.C.  From  the  points  1,  2,  3,  &.C.,  in  the  semicircular  arc,  draw 
straight  lines  1 k,  2 /,  3 m,  &.C.,  perpendicular  to  A C.  From  the  points  k,  /,  m, 
&.C.,  draw  straight  lines  A'E,  /E,  mE,  &.C.,  intersecting  the  curve  A C in  q,  r, 
&c.  Draw  the  straight  lines  p t,  qu,  r v,  &.C.,  parallel  to  one  side,  E C meeting 
A C in  the  points  t,  ii,  v,  &lc.  Also  from  the  points  1,  2,  3,  in  the  sectorial  arc 
A F,  draw  the  straight  lines  1 E,  2 E,  3 E,  &,c.  Transfer  the  distances  pt,  qu, 
rv,  &.C.,  to  1 a,  2 b,  3 c,  &lc.  ; then  through  the  points  A,  a,  h,  c,  &lc.,  draw  the 
curve  A c F,  and  A c F is  one  of  the  edges  of  the  development,  and  by  draw- 
ing the  other  edge,  the  entire  development  A G H F will  be  found. 


SECTION  V.  — Construction  of  the  Moulds  for  Horizontal  Cylindretic  Vaults,  either 

TERMINATING  RiGHTLY  OR  OBLIQUELY,  UPON  PlANE  OR  CYLINDRICAL  V'ALLS,  TVITH  THE 

Joints  of  the  Courses  either  in  the  Direction  of  the  Vault,  perpendicular  to  the 
Faces,  or  in  Spiral  Courses. 

DEFINITIONS  OF  MASONRY,  WALLS,  VAULTS,  &c. 

Stone-cutting  is  the  art  of  reducing  stones  to  such  forms  that  when  united 
ogether  they  shall  form  a determinate  whole. 


ON  WALLS  AND  VAULTS. 


107 


In  preparing  stones  for  walls,  of  which  their  surfaces  are  intended  to  be  per- 
pendicular to  the  horizon,  nothing  more  is  necessary  than  to  reduce  the  stone  to 
its  dimensions,  so  that  each  of  its  eight  solid  angles  may  be  contained  by  three 
plane  right  angles. 

Moreover,  in  working  the  stones  of  common  straight  right  cylindretic  vaults, 
where  the  planes  of  the  sides  of  the  joints  terminate  upon  the  intrados  or  ex- 
trados  of  the  arch  or  vault,  in  straight  parallel  ruled  lines  of  the  cylindretic 
surface,  there  can  be  no  difficulty  ; for  if  one  of  the  beds  of  the  stone  be 
formed  to  a plane  surface,  and  if  this  side  be  figured  to  the  mould,  and  the 
opposite  ends  squared,  and,  lastly,  the  face  or  vertical  moulds  applied  upon  the 
ends  thus  squared,  and  their  figures  drawn,  these  figures  will  be  the  two  ends 
of  a prism,  consisting  of  equal  and  similar  figures,  and  will  be  similarly  situated ; 
and  therefore  we  have  only  to  form  this  prism,  in  order  to  form  the  arch-stone 
required. 

But  the  formation  of  the  stones  in  the  angles  of  vaults,  and  in  the  courses 
of  spherical  niches  and  domes,  are  much  more  difficult,  and  require  more 
consideration.  In  such  constructions  various  methods  may  be  employed,  and 
some  of  these,  in  particular  instances,  with  great  advantage,  both  in  the  saving 
of  workmanship  and  material,  as  we  shall  have  occasion  to  show.  In  general, 
however,  previous  to  the  reducing  of  a stone  to  its  ultimate  form  for  such  a 
situation,  it  will  be  found  convenient  to  reduce  the  stone  to  such  a figure  as  w'ill 
include  the  more  complex  figure  of  the  stone  required,  so  that  any  surface  of 
the  preparatory  figure  may  either  include  a surface  or  arris  of  the  stone  re- 
quired to  be  formed,  or  be  a tangent  to  this  surface. 

Surfaces  are  brought  to  form  by  means  of  straight  and  curved  edges,  always 
applied  in  a plane  perpendicular  to  the  arris-lines,  so  that,  when  a surface  is 
thoroughly  formed,  the  edge  of  application  may  have  all  its  points  in  contact 
with  the  surface  in  its  whole  intended  breadth. 

A wall,  in  masonry,  is  a mass  of  stones  or  other  material,  either  joined  to- 
gether with  or  without  cement,  so  as  to  have  its  surfaces  such  that  a plumb- 
line,  descending  from  any  point  in  either  face,  will  not  fall  without  the  solid. 

One  of  the  faces  of  a wall  is  generally  regulated  by  the  other,  and  the  reg- 
ulating surface  is  called  the  principal  face. 

The  line  of  intersection  of  the  principal  face  of  a wall  and  a horizontal  plane 
on  a level  with  the  ground,  or  as  nearly  so  as  circumstances  will  permit,  is  called 
the  base-line. 

A horizontal  section  of  a wall,  through  the  base-line,  is  called  the  seat  of  the 
wall. 

The  other  side  of  the  seat  of  a wall,  opposite  to  the  base-line,  is  called  the 
rear-line. 


108 


PRACTICAL  MASONRY. 


In  exterior  walls  the  outer  surface  is  always  the  principal  face,  and  the  base 
and  rear-lines  are  generally  so  situated,  that  normals  drawn  to  the  base-line, 
between  the  base  and  rear-lines,  are  all  equal  to  one  another.  This  uniform- 
ity most  frequently  takes  place  also  in  partition  or  division  walls  ; but,  in  some 
instances,  on  account  of  a room  being  circular  or  elliptical,  while  the  other  faces 
are  plane  or  curved  surfaces,  this  equality  of  the  normals  cannot  subsist. 

If  a wall  be  cut  by  a plane  perpendicular  to  the  base-line,  or  if  the  base-line 
be  a curve  perpendicular  to  a tangent  through  the  point  of  contact,  such  a sec- 
tion is  called  a right  section. 

Hence,  according  to  this  definition,  since  the  base-line  is  always  in  a horizon- 
tal plane,  every  straight  line  and  every  tangent  to  a base-line,  when  it  is  a curve, 
will  be  a horizontal  line,  therefore  the  right  section  must  be  in  a vertical  plane. 

Walls  are  denominated  according  to  the  figure  of  their  base-line.  When  the 
base-line  is  straight,  the  wall  is  said  to  be  straight.  Hence,  if  the  figure  of  the 
base  be  an  arc  or  the  whole  circumference  of  a circle,  or  a portion  or  the  entire 
curve  of  an  ellipse,  the  wall  is  said  to  be  circular  or  elliptical.  Other  forms  sel- 
dom occur  in  building. 

Walls  are  more  strictly  defined  by  the  joint  consideration  of  the  figures  of 
their  bases  and  right  section. 

When  the  base  and  the  right  section  of  a wall  are  each  a straight  line,  and 
all  the  horizontal  sections  straight  lines,  the  face  of  the  wall  is  called  a ruler 
surface,  and  if  all  the  right  sections  have  the  same  inclination,  the  wall  is  called 
a straight  inclined  wall ; if  they  are  all  vertical,  the  wall  is  called  an  erect  straight 
wall,  or  a vertical  straight  wall.  If  the  right  sections  vary  their  inclination,  the 
wall  is  called  a winding  wall. 

When  the  base-line  is  the  circumference  or  any  arc  of  a circle,  and  the  right 
section  a straight  line  perpendicular  to  the  horizon,  the  wall  is  said  to  be  cylin- 
dric.  If  the  right  sections  of  a wall  be  all  equally  inclined  to  the  horizon,  the 
wall  is  said  to  be  conic ; and  thus  a wall  takes  also  the  name  by  which  its  sur- 
face is  called ; hence  a straight  wall,  which  has  its  right  sections  either  vertical 
or  at  the  same  inclination,  is  called  a plane  wall. 

A wall  in  tallus,  or  a battering  icall,  is  that  of  which  the  vertical  section  of  the 
principal  face  is  a straight  line  not  perpendicular  to  the  horizon.  This  vertical 
section  is  called  the  tallus-line. 

The  horizontal  distance  between  the  foot  of  the  tallus-line  and  the  plumb- 
line,  passing  through  its  upper  extremity,  is  called  the  quantity  of  hatter ; and 
the  plumb-line,  from  the  top  of  the  tallus-line  to  the  level  of  its  foot,  is  called 
the  vertical  of  the  baiter. 

The  interstices  between  the  stones,  for  the  insertion  of  cement  or  mortar,  in 


* A'  ^ 


/r  fK  M/f  0/1  Sc. 


PI 


o. 


ON  OBLIQUE  ARCHES. 


109 


order  to  connect  the  stones  into  one  solid  mass,  are  called  joints,  and  the  sur- 
faces of  the  stones  between  which  the  mortar  is  inserted  are  called  the  sides  of 
the  joints. 

When  the  sides  of  the  joints  are  everywhere  perpendicular  to  the  face  of  a 
wall,  and  terminate  in  horizontal  planes  upon  that  face,  such  joints  are  called 
coursing-joints ; and  the  row  of  stones  between  every  two  coursing-joints  is 
called  a course  of  stones. 

An  arch  or  vault,  in  masonry,  is  a mass  of  stones  suspended  over  a hollow, 
and  supported  by  one  or  more  walls  at  its  extremities,  the  surface  opposed  to 
the  hollow  being  concave,  and  such  that  a vertical  line,  descending  from  any 
point  in  the  curved  surface,  may  not  meet  the  curved  surface  in  another  point. 

The  concave  surface  under  the  arch  or  vault  is  called  the  intrados  of  that  arch 
or  vault ; and  if  the  upper  surface  be  convex,  this  convex  surface  is  called  the 
extrados. 

Those  joints  which  terminate  upon  the  intrados  in  horizontal  lines  are  called 
coursing-joints,  and  the  coursing-joints  will  either  be  straight,  circular,  or  elliptic, 
according  as  the  horizontal  sections  of  the  intrados  are  straight,  circular,  or 
elliptic. 

Whether  in  walling  or  in  vaulting,  the  joints  of  the  stones  should  always  be 
perpendicular  to  the  face  of  the  wall,  or  to  the  intrados  of  the  arch,  and  the  joints 
between  the  stones  should  either  be  in  planes  perpendicular  to  the  horizon,  or  in 
surfaces  which  terminate  upon  the  face  of  the  wall  or  intrados  of  a vault  in  hori- 
zontal planes  ; these  positions  being  necessary  to  the  strength,  solidity,  and 
durability  of  the  work. 

Walls  and  vaults  being  of  various  forms,  namely,  straight,  circular,  and  elliptic, 
depending  on  the  plan  of  the  work ; hence  the  construction  will  depend  upon 
the  simple  figure  or  upon  the  complex  figure  when  combined  in  two. 


SECTION  VI.  — On  Oblique  Arches. 

PROBLEM  I. 

To  execute  an  oblique  cylindroidic  arch,  intersecting  each  side  of  the  wall  in  a 
semicircle,  the  imposts  of  the  arch  being  given. 

Let  fig.  2,  Plate  V.,  be  the  elevation,  and  in  fig.  5,  let  A B C D,  E F G H,  be 
the  two  imposts  which  are  equal  and  similar  parallelograms,  having  the  sides  A B, 
FE,  one  of  each  in  a straight  line,  and  the  sides  D C and  GH  in  a straight  line. 
Join  G C,  and  on  G C,  as  a diameter,  describe  the  semicircle  G I C,  which,  if 


110 


PRACTICAL  MASONRY. 


conceived  to  be  turned  upon  the  line  G C as  an  axis,  until  its  plane  become 
perpendicular  to  the  seat  B C GF  of  the  soffit  of  the  arch,  it  will  be  placed  in  its 
due  position.  Divide  the  semicircular  arc  GIG  into  as  many  equal  parts  as  the 
ring -stones  are  to  be  in  number.  We  shall  here  suppose  there  are  to  be  nine 
ring-stones.  From  the  points  of  division  1,  2,  3,  &,c.,  draw  ordinates  perpendic- 
ular to  G C,  meeting  G C in  the  points  p,  q,  r,  &c.  Perpendicular  to  C B,  the 
jamb-line  of  the  impost,  draw  the  lines  pi,  q2,  r 3,  &,c. ; from  the  point  C as  a 
centre,  with  the  chord  of  one  ninth  part  of  the  semicircular  arc,  C I G',  describe  an 
arc  intersecting  /)  1 C B at  1 ; from  the  point  1,  with  the  same  radius,  describe  an 
arc  intersecting  the  line  9 2 in  the  point  2 ; from  the  point  2,  as  a centre,  with  the 
same  radius,  describe  an  arc  intersecting  the  line  r 3 in  the  point  3 ; and  so  on. 
Join  the  point  C and  1 ; 1 and  2 ; 2 and  3,  &c.,  and  thus  form  the  entire  edge 
C K L of  the  development  of  the  semicircular  arc  GIG. 

Through  the  points  1,  2,  3,  &c.,  in  G K L,  draw  the  lines  I j3,  2 y,  3 d,  &lc., 
parallel  to  C B,  and  make  \ (3,  2 y,  3 8,  &.C.,  each  equal  to  C B ; and  join  B (3,  /3  y, 
y 8,  &,c. ; then  G B /3  1 is  the  soffit  of  the  first  ring-stone ; 1 /3  2 is  the  soffit  of 
the  second  ring-stone  ; 2^53,  the  soffit  of  the  third  ring-.stone ; and  so  on. 

Perpendicular  to  G F draw  F J ; produce  C B to  J ; and,  parallel  to  C J,  draw 
p s,  q t,  rii,  &LC.  Intersecting  F J in  the  points  v,  w,  x,  &.C.,  make  v s,  w t,  x u, 
&c.,  respectively  equal  to  /j  1,  </2,  r3,  &.c.  Join  J and  s,  s and  /,  / and  v,  &c. ; 
and  complete  the  polygonal  line  J u F.  Through  the  points  s,  t,  u,  &c.,  draw 
the  joint  lines  sij,  t z,  \i  O,  radiating  to  the  point  0 ; then  will  the  angles  of  incli- 
nation of  the  beds  and  soffits  be  X 3 s,  y s J,  the  first  ring-stone ; y s t,  z t s,  for 
the  second  ring-stone;  ztv,  Out,  for  the  third  ring-stone;  and  so  on. 

From  any  point  B in  EC,  l,make  the  angle  CBA  equal  to  the  angle 
A B C of  the  impost,  5.  Prolong  C B to  E.  From  B as  a centre,  with  any 
radius,  describe  the  semicircular  arc  C D E ; and  on  B C as  a diameter,  describe 
another  semicircular  arc  C ^ B.  Divide  the  semicircular  arc  C D E,  in  the  points 
1,  2,  3,  &.C.,  into  nine  equal  parts,  equal  to  the  number  of  ring-stones,  and  draw 
the  radials  1 B,  2 B,  3 B,  &,c.,  intersecting  the  semicircular  arc  C^B  in  the  points 
/,  g,  h.  See.  Draw  C A perpendicular  to  B C ; and  in  B A,  as  a diameter,  de- 
scribe the  semicircular  arc  B C A.  From  the  point  B,  with  the  radii  B/,  B^,  B A, 
&.C.,  describe  the  arcs  /i,  g k,  h /,  &.C.,  meeting  the  semicircular  arc  B C A in  the 
points  /,  k,  I,  Sec.,  and  draw  the  straight  lines  B i,  B k,  B /,  &.c.  Then,  A B G 
being  the  angle  of  the  impost,  A B i will  be  the  angle  of  the  joints  at  the  junction 
of  the  first  and  second  ring-stones  ; ABA*  the  angle  of  the  joints  at  the  junction 
of  the  second  and  third  ring-stones  ; AB  / will  be  the  angle  of  the  joints  at  the 
junction  of  the  third  and  fourth  ring-stones,  &,c. 

To  apply  the  moulds  for  cutting  any  one  of  the  ring-stones,  or  to  form  the 


ON  OBLIQUE  ARCHES. 


Ill 


solid  angles  made  by  the  face,  the  two  beds,  and  the  soffit  of  the  stone,  which 
being  done  will  form  that  ring-stone.  — For  instance,  let  it  be  required  to  form 
the  third  ring-stone;  — We  have  given  the  plane  angle  2y8,fig.  2,  which  is  a 
side,  and  the  plane  angle  k,  jig.  1,  another  adjacent  side;  also  the  angle 
z til,  Jig.  5,  which  is  the  inclination  of  these  two  sides,  to  construct  the  solid 
angle.  This  can  be  easily  done  by  working  the  bed  of  the  stone  corresponding 
to  the  joint  2 / on  the  soffit.  Jig.  5 ; then  work  the  narrow  side  of  the  stone,  from 
which  the  soffit  is  to  be  formed,  first  as  a plane  surface,  making  an  angle  z t ii 
with  the  bed  first  wrought ; place  the  surface  of  the  mould  abed,  Jig.  4,  upon 
the  narrow  side  of  the  stone  which  is  to  form  the  soffit,  so  that  the  edge  a b may 
be  upon  the  arris  of  the  stone  ; then,  by  the  edge  b c,  draw  a line ; again,  upon 
the  wrought  side  which  is  intended  for  the  bed  apply  the  angle  A B k,Jig.  1,  so 
that  the  line  A B may  be  upon  the  arris,  and  the  point  B on  the  same  point  that  b 
was  applied ; then  by  the  leg  B k,  which  is  supposed  to  be  upon  the  surface  of 
the  bed,  draw  a line ; we  have  only  to  cut  away  the  superfluous  stone  on  the 
outside  of  the  two  lines  on  the  bed  and  on  the  soffit ; and  thus  we  shall  form  a 
complete  trehedral ; the  plane  soffit  of  the  stone  being  gauged  to  its  breadth,  and 
the  mould  2 e dS,  Jig.  2,  being  applied  upon  the  last  wrought  side,  so  that  the 
points  d,  e,  may  be  upon  the  points  of  the  stone  to  which  b and  c were  applied ; 
then,  drawing  a line  by  the  edge  d 3,  and  cutting  away  the  superfluous  stone 
between  the  two  lines  on  the  front,  and  on  the  plane  of  the  soffit,  will  form  the 
upper  bed  of  the  stone. 

This  will  be  made  sufficient!}'  evident  by  a development  of  the  soffit,  the  two 
beds,  and  the  front  of  the  ring-stone.  Make  an  equal  and  similar  parallelogram 
abed,  fig.  4,  to  that  of  2 y 8 S,  fig.  5.  Make  the  angles  a be,  deg,  fig.  4,  re- 
spectively equal  to  the  angles  A B A B I,  fig.  1 ; then  b e being  equal  to  de,fig. 
2,  apply  the  mould  2 deS  so  that  the  points  d,  e,  may  be  upon  b e,  fig.  4,  and 
draw  the  front  of  the  stone  b e k i,  fig.  4,  and  similarly  draw  a din  1.  Make  b e 
equal  to  b i,  e g equal  to  e k,  and  draw  e f and  gh  parallel  io  ba  ov  ed,  and  this 
will  complete  the  development. 

A complete  model  of  the  stone  will  instantly  be  formed,  by  revolving  the  four 
sides  ab  ef,  b eki,  e dhg,  dalm,  upon  the  four  lines  b a,  be,  e d,  da,  as  axes, 
until  e coincide  with  i,  k with  g,  h with  m,  and  / with  f. 

We  have  here  made  use  of  the  development  of  the  in  trades  in  the  construc- 
tion of  the  solid  angles,  as  being  easily  comprehended.  The  ring-stones  might, 
however,  have  been  formed  by  the  angle  of  the  joints,  which  is  one  side  of  a 
trehedral ; one  of  the  angles  of  the  face  mould,  which  is  the  other  adjacent  side ; 
and  the  inclination  of  these  two  sides ; so  that  we  shall  have  here  also  two  sides 
and  the  contained  angle,  to  construct  the  solid  angle  of  the  trehedral.  As  an 


112 


PRACTICAL  MASONRY. 


example,  let  it  again  be  required  to  construct  the  third  ring-stone.  To  find  the 
angle  which  the  face  of  the  third  ring-stone  makes  with  the  bed  in  the  second 
joint : — We  have  here  given  the  two  legs  A B C,  C B 2,^^.  1,  of  a right-angled 
trehedral,  to  find  the  angle  which  the  hypothenuse  makes  with  the  side  C B 2 ; 
this  being  found,  will  be  the  inclination  of  the  face-mould  2de3,  Jig.  2,  and 
A B k,  Jig.  1.  Therefore,  in  this  case,  work  the  bed  of  the  stone  first,  then  the 
face,  to  the  angle  of  inclination  thus  found.  Upon  the  arris  apply  the  leg  A B of 
the  joint  mould  A B k,Jig.  1,  so  that  the  side  B k may  be  upon  the  bed,  and 
draw  a straight  line  on  the  bed  by  the  edge  B /c ; next  apply  the  mould  2 d e3, 
so  that  the  arc  d 2 may  be  upon  the  arris,  and  the  point  d upon  the  same  point 
of  the  arris  to  which  the  point  B was  applied,  and  the  chord  d e upon  the  face ; 
then  draw  a line  on  the  face  of  the  stone,  by  the  leg  de  ; and  work  off  the 
superfluous  stone ; and  the  face  will  be  exhibited.  Fig.  3 shows  the  stone  as 
wrought. 

From  what  has  been  said,  it  is  evident  that  if  one  of  the  solid  angles  of  a ring- 
stone  be  formed  of  an  oblique  arch  in  a straight  wall,  the  remaining  solid  angle 
may  be  formed  without  the  use  of  the  trehedral.  Thus,  for  instance,  suppose  the 
solid  angle  which  is  formed  be  made  by  the  surface  of  the  soffit,  the  bed,  and 
the  face  of  the  arch : — we  have  only  to  gauge  the  soffit  to  its  breadth,  and  apply 
the  head-mould  upon  the  face  of  the  stone ; then,  by  working  off  tbe  superfluous 
stone  between  these  lines,  another  solid  angle  will  be  formed  by  the  surface  of 
the  soffit,  the  upper  bed  of  the  stone,  and  the  face  of  the  arch. 

And  since  the  angle  of  the  joints  is  the  same  in  the  lower  and  upper  beds  of 
any  two  ring-stones  that  come  in  contact  with  each  other,  the  same  angle  of  the 
joints  will  do  for  both,  so  that,  in  fact,  if  this  be  carried  from  one  ring-stone  to 
another,  the  arch  may  be  executed  without  any  joint  mould. 

This  mode  would,  however,  not  only  be  inconvenient,  but  liable  to  very  great 
inaccuracy.  It  would  be  inconvenient,  as  it  is  necessary  to  work  one  stone 
before  another,  so  that  only  one  workman  could  be  employed  in  the  construction 
of  the  arch.  It  would  be  liable  to  inaccuracy  when  the  number  of  ring-stones 
are  many,  for  then  any  small  error  would  be  liable  to  be  multiplied  or  transmitted 
from  one  stone  to  another.  Besides,  it  is  satisfactory  to  have  a mould  to  apply, 
in  order  to  examine  the  work  in  its  progress. 

What  has  been  now  observed,  with  regard  to  the  oblique  arch  in  a straight 
wall,  and  with  respect  to  the  angle  on  the  edges  of  the  point,  will  apply  to  every 
arch  of  which  the  intrados  is  a cylindric  or  cylindroidic  surface. 

In  the  construction  of  any  object,  it  is  always  desirable  to  have  two  different 
methods,  as  one  may  always  be  a proof  or  check  to  the  other.  Besides,  though 


ON  OBLIQUE  ARCHES. 


113 


these  methods  may  be  equally  true  in  principle,  one  of  them  may  be  often  liable 
to  greater  inaccuracy  in  its  construction  than  the  other. 

PROBLEM  II. 

To  construct  the  moulds  for  a cylindretic  oblique  arch  terminating  upon  the 
face  of  a wall  in  a plane  at  oblique  angles  to  the  springing  plane  of  the  vault,  so 
that  the  coursing-joints  may  be  in  planes  parallel  to  the  ruler  lines  of  the  intrados 
of  the  vault. 

Let  the  vertical  plane  of  projection  be  perpendicular  to  the  axis  of  the  intrados, 
and  it  will  therefore  be  also  perpendicular  to  all  the  joints  of  which  their  planes 
are  parallel  to  the  axis ; hence,  — 

The  vertical  projection  of  the  intrados  will  be  a curve  equal  and  similar  to  the 
curve  of  the  right  section  of  the  intrados. 

The  vertical  projections  of  the  coursing-joints  will  be  radiant  straight  lines,  in- 
tersecting the  curve-lined  projection  of  the  intrados. 

The  vertical  projections  of  all  the  joints  which  are  in  vertical  planes  parallel  to 
the  axis  will  be  straight  lines  perpendicular  to  the  ground-line. 

The  vertical  projection  of  all  the  joints  m,  horizontal  planes,  will  be  straight  lines 
parallel  to  the  ground-line. 

Moreover,  the  vertical  projections  of  the  intersections  of  planes  which  are  par- 
allel to  the  axis  will  be  points.  ‘ 

The  horizontal  projections  of  the  planes  of  the  coursing-joints,  and  of  all  the 
intersections  of  the  planes  of  all  joints  which  are  parallel  to  the  axis,  will  be 
straight  lines  perpendicular  to  the  ground-line. 

And  because  the  axis  of  the  archant  is  perpendicular  to  the  vertical  plane,  the 
vertical  projections  of  the  intrados,  and  of  the  joints  which  are  parallel  to  the  axis, 
will  have  the  same  position  to  one  another,  as  the  curve  and  other  lines  in  the 
right  section  which  are  formed  by  the  joints  in  planes  parallel  to  the  axis. 

All  sections  which  are  perpendicular  to  the  horizon  will  have  straight  lines  for 
their  horizontal  projections. 

The  length  of  any  inclined  line  will  be  to  the  length  of  its  projection,  as  the 
radius  is  to  the  cosine  of  the  line’s  inclination  to  the  plane  of  projection. 

We  shall  suppose  that  the  stones  which  constitute  the  intrados  of  the  archant 
have  not  fewer  than  three,  nor  more  than  four,  of  their  faces  that  intersect  the  in- 
trados. The  stones  which  form  the  face  of  the  archant,  when  they  do  not  reach 
the  rear  of  the  vault,  have  three  of  their  faces  which  intersect  the  intrados,  and 
three  at  least  which  intersect  the  face. 

We  shall  call  all  these  surfaces,  which  intersect  the  intrados  or  face  of  the 
15 


114 


PRACTICAL  MASONRY. 


archant,  the  retreating  sides  of  joints  of  the  stones  ; and  the  surface  of  any  stone 
which  forms  a part  of  the  intrados,  the  douelle  of  the  stone. 

When  the  stones  do  not  reach  from  the  front  to  the  rear  of  the  intrados  of  an 
archant,  they  are  arranged  in  rows,  in  such  a manner,  that  the  stones  which  con- 
stitute any  one  of  the  rows  have  as  many  of  their  retreating  sides  as  there  are 
stones  in  the  row  in  one  continued  surface,  and  the  opposite  retreating  sides  of 
all  the  stones  in  another  continued  surface,  while  the  heads  form  a portion  of  the 
intrados  extending  from  front  to  rear  of  the  vault,  and  the  remaining  retreating 
sides  of  the  stones  either  come  in  contact,  or  are  connected  together  by 
mortar. 

Every  such  row  of  stones  is  called  a course  of  vaulting. 

One  course  may  be  joined  to  another  by  bringing  their  adjacent  continued  sur- 
faces in  contact ; but  they  are  generally  cemented  with  mortar,  which  is  called 
the  coursing-joint,  and  as  this  cementing  substance  should  be  as  thin  as  possible, 
and  of  an  equal  thickness,  we  shall  suppose  that  the  coursing-joints  intersect  the 
intrados  in  lines  extending  from  front  to  rear  of  the  vault,  and  we  shall  call 
these  lines  the  coursing  lines  of  the  intrados. 

In  this  example,  as  the  vertical  projection  of  the  intrados,  and  of  the  joints 
which  are  in  planes  parallel  to  the  axis,  are  identical  in  all  respects  to  the  lines  of 
the  right  section,  the  dimensions  between  every  two  corresponding  points  being 
equal  in  both,  w^e  may  therefore  substitute  at  once  the  right  section  for  the  verti- 
cal projection,  placing  the  right  section  upon  the  ground-line  U V. 

Plate  XI.  Let  No.  1 be  the  right  section  placed  in  the  situation  of  the  ver- 
tical plane  projection  upon  the  ground-line  U V,  the  curve  line  C O C'  being  the 
vertical  projection  of  the  intrados,  A D,  B F,  C H,  the  projections  of  the  vertical 
projection  coursing-joints,  meeting  the  projection  of  the  intrados  in  the  points 
A,  B,  C.  Of  these  radiant  lines  C H is  the  projection  of  the  springing.  The 
line  B F meets  the  line  F G parallel,  and  E F perpendicular,  to  the  ground-line 
U V.  The  extrados  ZEDY  of  this  section  is  a straight  line  parallel  to  the 
ground-line.  As  this  right  section  of  this  vault  is  symmetrical,  we  shall  only  de- 
scribe one  half ; the  other  will  be  understood  by  the  same  rules. 

Let  r s,  No.  2,  be  the  trace  of  the  vertical  face  of  the  wall  on  the  horizontal 
plane  of  projection,  making  a given  angle  with  the  ground-line  U V,  and  let  u v 
and  r s be  the  traces  of  the  inclined  face  of  the  wall ; the  inclination  of  this  face 
being  given  by  a right  section  of  the  wall. 

Let  r zi  ATI,  No.  3,  be  the  right  section  of  the  wall,  of  which  A U,  the  base, 
is  equal  to  the  shortest  distance  between  the  two  traces  uv  and  rs,  No.  2,  of  the 
faces  of  the  wall.  The  line  II F oi  this  section  is  the  section  of  the  vertical 
face,  and  A J that  of  the  inclined  face  of  the  wall. 


ON  OBLIQUE  ARCHES. 


115 


This  section  FA  J II,  No.  3,  is  so  situated,  that  the  base  line  AU\?,  perpen- 
dicular to  the  traces  u v,  r s,  of  the  faces  of  the  wall,  No.  2,  the  point  II  being  in 
the  line  r s,  or  sr  prolonged,  therefore  the  point  A in  the  line  uv,  or  v u prolonged, 
and  n I'  being  perpendicular  io  A II  will  be  in  the  same  straight  line  with  the 
horizontal  trace  r s of  the  vertical  face  of  the  wall. 

In  order  to  obtain  the  projection  of  the  intersection  of  the  intrados  and  of  the 
joints  which  are  in  planes  parallel  to  the  axis  of  the  intrados  with  the  inclined 
face  of  the  wall,  we  must  find  the  projection  of  every  line  in  this  inclined  face 
made  by  the  intersection  of  a horizontal  plane  passing  through  every  point  in  the 
right  section  which  is  formed  by  every  two  lines  in  its  construction. 

For  this  purpose  it  will  be  necessary  to  find  the  horizontal  projection  of  every 
point  of  the  lines  where  the  intersections  of  the  planes  parallel  to  the  axis  meet 
the  inclined  face  of  the  wall.  To  proceed  : — 

Take  all  the  heights  of  the  points  of  the  right  section,  and  apply  them  respect- 
ively from  the  point  77  in  the  line  TIT,  No.  3;  through  these  points  draw  lines 
parallel  to  A 77,  so  that  each  line  may  meet  the  sloping  line  A J.  From  each  of 
the  points  in  the  line  A A draw  lines  parallel  to  the  horizontal  trace  u v,  No.  2, 
and  lines  being  drawn  from  the  corresponding  points  of  the  right  section  will 
give  the  points  required  by  the  intersection  of  the  two  systems  of  parallel 
lines. 

Thus,  to  find  the  horizontal  projection  of  the  intersection  of  any  particular  line 
which  is  parallel  to  the  axis  with  the  inclined  face  of  the  wall,  this  line  being 
given  by  its  intersecting  point  in  the  right  section.  No.  1 ; this  point  being  the  in- 
tersection of  one  of  the  coursing  lines,  namely,  the  first  A from  the  middle  of 
the  section  No.  1. 

Draw  A a perpendicular  to  the  ground-line,  and  transfer  the  height  K A of  the 
point  A,  No.  1,  upon  the  line  77 T",  No.  3,  from  77  to  1.  Draw  1-2  parallel  to 
U A,  A A meeting  P Q in  2.  From  2 draw  2 a parallel  to  either  of  the  horizon- 
tal traces  uv,  or  r s.  No.  2,  and  the  point  a (No.  2)  is  the  horizontal  projection 
of  the  extremity  of  the  coursing  line  of  the  intrados  which  passes  through  the 
point  A of  the  right  section. 

In  the  same  manner  may  be  found  the  projections  b and  c of  the  intersections 
of  the  coursing-joints  of  the  intrados,  with  the  face  of  the  archant,  and  also 
those  of  the  intersections  of  the  planes  parallel  to  the  axis ; the  projections  of 
these  points  being  exhibited  by  Italic  letters  corresponding  to  those  of  the  Ro- 
man in  the  right  section. 

To  find  the  development  of  the  intrados  or  soffit  of  the  arch. 

Parallel  to  the  ground-line  in  No.  2,  draw  the  regulating  line  5 f in  the  hori- 


116 


PRACTICAL  MASONRY. 


zontal  plane  of  projection,  intersecting  the  projections  aa\  hh\  cc\  &lc.  of  the 
coursing-joint  lines  in  the  points  a,  /3,  y,  &c. 

In  any  convenient  situation,  No.  4,  draw  the  line  V W,  and  in  V W take  any 
convenient  point  o.  In  o V make  o a equal  to  O A,  No.  1,  the  half-chord  of  the 
arc  of  the  section  of  the  key-course ; and  in  No.  4,  make  aji,  (i  y,  &,c.,  equal  to 
the  succeeding  chords  A B,  B C,  &c..  No.  1,  of  the  sections  of  the  courses  in  in- 
trados. 

Through  the  points  a,  (3,  y,  No.  4,  draw  the  lines  aa\  b b',  c c,  perpendicular  to 
V W,  and  make  aa,  ^ b,  y c,  respectively  equal  to  a a,  (3  b,  yc,  No.  2,  as  also  a a 
/3  b\  yc.  No.  4,  equal  to  a a',  (3  b\  y c,  No.  2.  In  No.  4,  join  ab,  be,  on  the  one 
side,  and  ab',b'c,  on  the  other;  then  aa'b'b,  bb'c'c,  will  be  the  chord-planes 
of  the  soIRts  of  the  courses  of  the  stones  on  each  side  of  the  key-course.  The 
figures  of  the  chord-planes  of  the  right-hand  side  of  the  arch  being  found  in  the 
same  manner,  will  give  the  entire  development  of  the  intrados  by  joining  the 
corresponding  ends  of  the  chord-plane  of  the  key-course. 

Through  any  convenient  point  V,  No.  4,  in  the  line  V W,  draw  a c perpen- 
dicular to  V W,  and  prolong  W V to  D.  Make  V D equal  to  A D,  No.  1,  and 
through  D,  No.  4,  draw  d d'  parallel  to  a c.  In  a c.  No.  4,  make  V a,  V a',  re- 
spectively equal  to  a a,  a a.  No.  2,  and  make  D d,  D d'.  No.  4,  respectively 
equal  to  \ d,  \ d'.  No.  2.  Join  a d,  a d',  then  will  a a'd'd.  No.  4,  be  the  side  or 
figure  of  the  coursing-joint  corresponding  with  the  line  A D,  No.  1.  In  the 
same  manner  the  remaining  figures  bbTf,  cc'hli,  will  be  found,  as  also  the 
remaining  figures  of  the  coursing-joints  on  the  right  hand  side. 

Then  the  figures  of  the  moulds  for  the  course  of  stones,  of  which  the  right 
section  is  a figure  equal  and  similar  to  A B F E D,  No.  1,  are  No.  1,  and  aa'b'b, 
a a'd'd,  b bTf,  No.  4.  All  the  stones  are  wrought  to  the  form  of  right  prisms 
before  the  heads  in  the  front  and  rear  of  the  arch  are  formed,  then  the  moulds 
of  the  upper  and  lower  beds  are  applied,  and  their  figures  are  drawn  upon  the 
surfaces  of  the  coursing-joints,  so  as  to  give  the  intersections  of  the  coursing- 
joints  with  the  face  of  the  arch. 

In  the  course  of  stones  on  the  left  hand,  next  to  the  key-course  aa'b'b.  No.  4, 
is  the  chord-figure  of  the  intrados,  a a'd'd.  No.  4,  the  upper  bed,  and  b b'ff  the 
lower  bed. 

To  find  any  point  in  the  oblique  face  of  the  arch.  Let  the  point  to  be  found 
be  the  point  corresponding  to  the  point  A. 

The  place  of  the  point  A in  the  oblique  line  A A,  No.  3,  is  at  the  point  2,  and 
its  place  upon  the  projection  No.  2 is  at  a.  Draw  A T perpendicular  to  A v,  or 
to  uv,  and  in  A T make  A 2 equal  to  A 2 in  AJ.  From  the  point  2,  in  A T, 


/V  6'. 


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ON  OBLIQUE  ARCHES. 


117 


draw  2p  parallel  to  u v,  and  draw  ap  perpendicular  to  ii  v,  and  the  point  jo  will 
be  in  the  curve  of  the  oblique  face  of  the  arch. 

In  the  same  manner  will  be  found  the  points  i,  q,  &lc.,  in  the  curve  of  the 
oblique  face  of  the  arch,  as  also  all  other  points,  by  first  finding  their  projections 
as  at  No.  2,  and  the  heights  of  these  points  upon  the  oblique  line  ^z/.  No.  3, 
and  then  transferring  the  points  thus  found  upon  the  perpendicular  ^ T. 
Through  the  points  found  in  the  perpendicular  zi  T,  draw  lines  parallel  to  m v,  to 
intersect  with  lines  drawn  perpendicular  to  n v from  the  projections  of  the  points 
to  be  found  in  No.  2,  and  the  points  of  intersection  of  every  two  lines  will  be 
the  points  in  the  oblique  face  of  the  arch  corresponding  to  those  in  the  section 
No.  1. 

The  curve  thus  found  in  the  oblique  face  of  the  arch  will  be  an  oblique  curve ; 
therefore  the  line  u v will  not  be  an  axis,  but  a diameter. 

To  find  the  direction  of  any  joint  in  the  oblique  face  of  the  arch,  the  plane 
of  the  joint  being  perpendicular  to  the  springing  plane  of  the  arch. 

Suppose,  for  instance,  the  plane  passing  through  LT  in  the  elevation  No.  1, 
perpendicular  to  U V.  Find  the  projection  t and  / in  the  horizontal  plane  of  pro- 
jection of  the  points  represented  by  T and  L in  the  vertical  plane  of  projec- 
tion, and  find  the  point  i in  the  curve  of  the  oblique  face  of  the  arch,  correspond- 
ing to  the  point  T in  the  vertical  plane  of  projection ; then  joining  the  points  / 
and  i,  the  straight  line  / i will  be  the  position  of  the  joint  in  a plane  perpendicu- 
lar to  the  springing  plane  of  the  intrados  of  the  arch. 

PROBLEM  HI. 

To  construct  an  oblique  arch  for  a canal  with  a cylindric  intrados,  so  that  the 
sides  of  the  coursing-joints  may  be  in  planes  which  intersect  each  other  in 
straight  lines  perpendicular  to  the  two  faces  of  the  arch,  and  parallel  to  the  hori- 
zon, and  that  the  planes  of  the  coursing-joints  may  make  equal  angles  with  each 
other: — 

Plate  VI.,  jig.  1.  Let  AB  CD  be  the  plane  of  the  arch  ; AD  and  BC  being 
the  planes  of  the  faces,  and  A B,  DC,  the  planes  of  the  springing  lines  of  the  in- 
trados of  the  arch  parallel  to  the  line  of  direction  of  the  canal. 

Find  the  middle  point  e of  the  parallelogram  A B C D,  and  draw  ef  perpendic- 
ular to  A D or  B C.  Through  any  convenient  point / in  c/  draw  G H perpendic- 
ular to  ef,  and  from  the  point  f,  with  a radius  equal  to  half  of  AD  or  B C,  de- 
scribe the  semi-circumference  ik  I meeting  G H in  i and  /.  Divide  the  circum- 
ference i k I from  i into  as  many  equal  parts  as  the  coursing-joints  are  intended  to 
be  in  number : for  example,  let  it  be  divided  into  nine  equal  parts,  i 1,  1 2,  23,  &c. 
Draw  the  tangent  Q R parallel  to  G H,  and  from  /,  and  through  the  points  1,  2 


118 


PRACTICAL  MASONRY. 


3,  &LC.,  of  division,  draw  the  straight  lines  / m,  / «,  / o,  fp,  &c.,  meeting  Q R in 
the  points  m,  n,  o,  p. 

Through  e draw  s t parallel  to  A B or  D C,  and  draw  m s,  n u,  o w,  p y,  per- 
pendicular to  G H,  meeting  5 f in  the  points  s,  u,  w,  y.  Make  e z,  ex,  e v,  et, 
equal  respectively  to  e y,  e w,  e ii,  e t.  Prolong  C D to  meet  efm  y,  and  prolong 
/ e and  A B to  meet  each  other  in  the  point  /3 ; then  with  the  two  diameters  s t 
and  /3  y describe  the  ellipse  s ^ t y,  and  with  the  two  diameters  uv  and  /3  y de- 
scribe the  ellipse  u (3  v y,  and  so  on  ; then  the  portions  of  these  curves  comprised 
between  the  lines  A D and  B C will  be  the  planes  of  the  coursing-joints. 

The  method  which  has  now  been  shown  for  finding  the  joint  lines  of  the  in- 
trudes of  the  arch  is  quite  satisfactory  as  to  the  principle,  since  it  exhibits  the 
planes  of  the  complete  sections  of  the  cylinder  by  the  cutting  planes  of  the  joints 
to  the  several  angles  of  inclination.  We  shall  show  how  the  joint  lines  of  the 
intrados  themselves  may  be  found,  as  depending  upon  the  planes  of  the  joints. 

To  find  the  plane  curves  for  the  joints  of  the  intrados  : — 

Having  found  the  conjugate  diameter  ^y,  and  the  semi-conjugate  es,  as  also 
the  semi-conjugate  diameter  e m,  e w,  ey,  Plate  3,  as  has  been  shown  in 

the  immediately  preceding  plate,  proceed  in  the  following  manner.  Draw  s t,uv, 
wx,  y z,  perpendicular  to  es,  and  make  s t,uv,  wx,  y z,  each  equal  to  the  radius 
of  the  semicircle  i k 1.  Join  e t,  e v,  e x,  e z.  Draw  s s',  u u,  w lo',  y y',  perpen- 
dicular to  ^ y or  (3  f;  and  from  the  point  e as  a centre,  with  the  radii  et,  ev, 
ex,  e z,  describe  the  arcs  t s',  v u',  x w',  zy'.  Join  e s',  e u',  c w',  e y. 

With  the  diameters  e s',  e u,  e w',  e y',  and  with  their  common  conjugate  /3  y, 
describe  the  semi-ellipsis  I3s'y,(3u'y,  j3  tv' y,  (3  y' y,  <Scc.,  then  the  portions  of 
these  curves  contained  between  the  lines  B C and  A D will  be  the  curve  lines  of 
the  joints  required. 

Let  A B C D,  fig.  2,  be  the  plane,  which  is  a parallelogram  as  before.  Divide 
A B into  any  number  of  equal  parts,  as,  for  example,  into  four,  at  the  points  1,2, 
3,  and  draw  the  lines  1 a,  2 /3,  3 y,  parallel  to  B C or  A D,  meeting  D C in  the 
points  a,  j3,  y,  and  let  hg  be  the  ground-line  of  the  elevation  ; then  A D,  1 a,  2 (3, 
3 y,  B C,  are  the  planes  of  semicircular  sections  of  the  intrados,  and  are  each  par- 
allel to  the  ground-line  hg,  the  elevations  of  these  planes  will  be  semicircles. 

These  elevations  being  described,  let  efg  be  the  elevation  to  the  plane  B C, 
k I tn  the  elevation  to  the  plane  2 /3  in  the  middle,  between  the  planes  B C and 
A D of  the  semicircular  sections  of  the  cylinder.  Let  c be  the  centre  of  the 
semicircular  arc  k I m,  and  divide  the  semicircular  arc  k I m into  as  many  equal 
parts  as  there  are  intended  to  be  courses  in  the  arch  ; for  example,  let  the  number 
of  courses  be  nine,  and  therefore  the  semicircular  arc  k I m must  be  divided  into 
nine  equal  parts,  in  the  points  1,  2,  3,  &.c. 


ON  OBLIQUE  ARCHES. 


119 


From  the  centre  c,  &c.,  and  through  the  points  of  division  1,  2,  3,  draw  lineis 
which  will  be  the  elevation  of  the  joints,  and  let  p t he  one  of  these  lines,  inter- 
secting the  five  semicircles  in  the  points  p,  q,  r,  s,  t.  Draw  the  lines  p u,  q v,  r w, 
s X,  tij,  perpendicular  to  the  ground-line  h g,  intersecting  the  planes  A D,  1 a,  2/3, 
3 B C',  in  the  points  u,  v,  ic,  x,  ij,  and  the  line  uvwxy  being  drawn,  will  be 
the  correct  plane  of  the  joint  required. 

In  the  same  manner  the  planes  of  the  remaining  joints  may  be  found. 

Let  lad,  fig.  4,  be  the  plane  of  one  pier,  and  ycf  the  plane  of  the  other  pier, 
ad  and  c/ being  the  planes  or  horizontal  sections  of  the  springing  lines  of  the  in- 
trados ; also,  let  L F be  the  ground-line  parallel  to  the  planes  of  the  front  and 
rear  elevations.  Describe  the  five  semicircles  in  the  elevation  as  before,  ABC 
being  that  in  the  front,  D E F that  in  the  rear,  and  G H I that  belonging  to  the 
middle  section. 

Divide  the  semicircular  arc  G H I into  the  number  of  equal  parts  required,  and 
let  the  points  of  division  be  1,2,  3,  &.c.  Through  the  points  1,  2,  3,  &c.,  draw 
the  straight  lines  lo,  2 s,  3 U,  &.C.,  radiating  to  the  centre  of  the  semicircular  arc 
A B C',  intersecting  the  curve  A B C in  the  points  N,  R,  T,  and  the  lines  N O, 
R S,  T U,  will  be  the  joint  lines  of  the  face,  and  will  be  perpendicular  to  the 
curve  line  ABC. 

In  the  straight  line  ac,  which  is  the  plane  of  the  face  of  the  arc,  take  a part  zn 
for  the  joint  in  the  direction  N O of  the  elevation,  and  let  the  lines  1 N,  2 R,  3 T, 
intersect  the  semicircular  arc  between  the  parallel  sections  ABC  and  D E F in 
the  points  &-c.  Let  the  points  w and  v be  in  the  straight  line  a c.  Make 

nu  and  iiv  respectively  equal  to  N a,  a 1,  and  draw  iiio  and  vx  perpendicu- 
lar to  zv. 

Divide  a d into  as  many  equal  parts  as  the  thickness  of  the  arch  is  divided 
into  equal  parts  by  the  planes  of  the  semicircular  arcs  which  are  parallel  to  the 
planes  of  the  front  and  rear  faces ; that  is,  divide  ad  into  four  equal  parts,  and 
let  a k,  a g,  be  two  of  those  parts  in  succession,  and  draw  k w and  g x parallel  to 
a c ; then  n,  w,  x,  will  be  three  points  in  the  curve  which  is  the  intersection  of 
the  plane  of  the  curving  joint  and  the  cylindric  surface  forming  the  intrados ; and 
thus  we  might  find  as  many  points  as  we  please,  by  increasing  the  number  of 
equidistant  sections.  This  gives  the  first  joint  next  in  succession  to  the  spring- 
ing A D. 

In  the  same  manner  all  the  other  coursing-joints  will  be  found  as  at  No.  2, 
No.  3,  No.  4,  &,c. 

Observations  on  the  preceding  methods  : — 

The  most  simple  construction  of  an  oblique  arch  with  a cylindrical  intrados  is 
that  where  the  sides  of  the  coursing-joint  are  in  plane  intersecting  the  intrados 


120 


PRACTICAL  MASONRY. 


perpendicularly  in  straight  lines,  as  in  the  first  example;  but  when  the  arch  is 
very  oblique,  the  coursing-joints  intersect  the  planes  of  the  two  vertical  faces  in 
very  oblique  angles. 

It  has  been  shown,  that  when  the  sides  of  the  coursing-joints  are  in  planes 
perpendicular  to  the  front  and  rear  faces,  these  planes  cut  the  intrados  very 
obliquely,  except  at  the  middle  section,  or  in  the  best  method  in  the  curve  of 
the  front  and  rear.  It  therefore  appears,  that  in  an  oblique  arch,  in  order  that 
the  surfaces  of  the  coursing-joints  may  intersect  both  the  intrados  and  the  face 
of  the  arch  perpendicularly,  the  sides  of  the  coursing-joints  cannot  be  in  planes. 

In  order  that  every  arch  may  be  the  strongest  possible,  a straight  line  pass- 
' ing  through  any  point  of  the  surface  of  a joint  perpendicularly  to  the  intrados 
ought  to  have  all  its  intermediate  points  between  the  point  through  which  it 
passes,  and  the  intrados,  in  the  surface  of  the  side  of  the  coursing-joint ; and 
in  order  that  the  stones  may  be  reduced  to  their  form  in  the  easiest  manner  pos- 
sible, the  surfaces  should  be  uniform ; and  the  forms  of  the  stones  should  be 
similar  solids,  and  the  solids  similarly  situated. 

To  obtain  these  desirable  objects  will  not  be  possible  where  the  faces  of  the 
arch  are  plane  surfaces  ; however,  even  in  this  case,  the  joints  may  be  so 
formed  by  uniform  helical  surfaces,  that  they  will  intersect  the  intrados  perpen- 
dicularly in  every  point,  and  the  faces  of  the  arch  perpendicularly  in  two  points 
of  the  curve. 

This  mode  of  executing  a bridge  renders  the  construction  much  stronger  than 
when  the  joints  of  it  are  parallel  to  the  horizon.  Since,  in  this  last  case,  the 
angles  of  the  beds  and  tbe  faces  are  so  acute  upon  one  side,  that  the  points  of 
the  ring-stones  are  very  liable  to  be  broken,  or  even  to  be  fractured  in  large 
masses. 

For,  though  the  gravitating  force  acts  perpendicularly  to  the  horizon  ; yet, 
notwithstanding,  when  one  body  presses  upon  the  surface  of  another,  the  faces 
act  upon  each  other  in  straight  lines  perpendicularly  to  their  surfaces.  Hence 
a right-angled  solid  will  resist  equally  upon  all  points  of  its  surface. 

From  this  consideration,  we  are  induced  to  give  a preference  to  the  constmc- 
tion  with  spiral  joints,  though  attended  with  greater  difficulty  in  the  execution. 

PROBLEM  IV. 

To  execute  a bridge  upon  an  oblique  plan,  with  spiral  joints  rising  nearly 
perpendicular  to  the  plane  of  the  sides. 

Fig.  7,  Plate  Y.,  is  the  plan  of  a bevel  bridge ; Jig.  6,  the  elevation  of  the 
same,  as  the  two  faces  of  the  obtuse  angle  are  shown ; the  joints  of  the  intrados 
descend  from  the  face  of  the  arch  in  such  a manner,  that  supposing  the  lines  a b 


\'k 


4f 


t - 


4 


V/. 


i 


\ 


-/  -.  V 


.w. 


ON  OBLIQUE  ARCHES. 


121 


ab\  a"h",fig.  6,  to  be  the  joints  of  the  intrados,  meeting  the  curve  of  the  inter- 
section of  the  face  of  the  arch  and  intrados  in  the  points  b,  b\  b'\  &c.,  then  the 
joints  b a,  b'a,  b"a  \ &lc.,  are  as  nearly  perpendicular  to  the  curve  b b'b"b'"  as 
possible  for  the  construction  to  admit  of,  supposing  the  joints  to  be  all  parallel  to 
each  other.  By  making  the  joints  of  the  intrados  all  parallel  to  each  other,  all 
the  intermediate  arch-stones  will  have  the  same  section  when  cut  by  a plane  at 
right  angles  to  the  arris-line  of  the  bed  and  intrados  of  the  arch ; therefore,  if 
the  intermediate  arch-stones  are  equal  in  length,  the  upper  and  lower  beds  must 
be  the  same  winding  surfaces,  and  consequently  must  all  coincide  with  each 
other,  and  all  the  end -joints  must  be  equal  and  similar  surfaces,  and  thus  all  the 
arch-stones  may  be  equal  and  similar  bodies. 

The  most  considerable  obliquity  of  the  joints  in  the  intrados  is  at  those  two 
parts  of  the  curve  where  it  meets  the  horizon.  The  obliquity  of  the  intradosal 
joints,  at  the  crown  of  the  arch,  is  considerably  less  than  at  the  horizon  ; but  in 
the  middle  of  that  portion  of  the  curve  between  the  crown  and  the  horizon  on 
each  side,  the  intradosal  joints  are  exactly  perpendicular  to  the  horizon. 

Had  it  not  been  for  these  deviations,  the  execution  of  this  arch  would  have 
been  extremely  easy,  and  very  few  constructive  lines  would  have  been  necessary. 

This  arch,  however,  might  be  executed  so  that  all  the  intradosal  joints  would 
be  perpendicular  to  the  curve  line  of  the  face  and  intrados  ; but  this  position 
would  have  caused  such  a diversity  in  the  form  of  the  stones  as  to  increase  the 
labor  in  a very  great  degree,  and,  consequently,  to  render  the  execution  very  ex- 
pensive ; and  not  only  so,  but  as  the  joints  would  have  been  out  of  a parallel, 
their  efl'ect  would  have  been  very  unsightly.  A succession  of  equal  figures, 
similarly  formed,  has  a most  imposing  effect  on  the  eye  of  the  spectator.  The 
laws  of  perspective  produce  on  the  imagination  a most  fascinating  variety,  the 
figure  only  varying  by  imperceptible  degrees,  which  yet  in  the  remote  parts 
produces  a great  change. 

There  is  still  another  method  in  which  the  greater  part  of  the  difficulty  may 
be  removed  without  impairing  the  strength  of  the  arch ; this  manner  is  to  form 
the  ring-stones  so  that  the  joints  in  the  intrados  may  be  perpendicular  to  the 
curve  forming  its  edge  ; the  intermediate  portion  of  the  intrados  to  be  filled  in 
with  arch-stones,  which  have  their  soffit-joints  parallel  to  the  horizon.  This 
disposition  of  the  joints  might  not  be  so  pleasant  to  the  eye,  but,  if  well  executed, 
it  could  not  be  disagreeable. 

If  the  ends  were  made  to  form  spirals,  as  in  jig.  8,  and  a wall  erected  above 
the  arch,  as  this  wall  could  only  be  made  to  coincide  in  three  points  at  most 
with  the  face  of  the  arch,  no  regular  form  of  work  could  be  introduced  so  as  to 
connect  the  wall  to  the  ring-stones. 

16 


124 


PRACTICAL  MASONRY. 


in  the  middle,  it  will  be  necessary  to  show  the  manner  of  finding  a tangent  in 
the  middle  of  the  curve.  For  this  purpose, — 

Make  the  angle  E A A:  equal  to  E A F,  and  let  the  point  m be  the  middle  of 
the  curve  D m A.  Through  the  point  m draw  p g parallel  to  k A,  and  pg  will  be 
the  tangent  required. 

In  like  manner,  make  the  angle  AH/ equal  to  A H G,  and  let  g be  the  middle 
point  of  the  curve  PI  g C ; through  g draw  r s parallel  to  H / and  rs  will  be  a 
tangent  to  the  curve  Hg-C. 

It  is  here  evident  from  the  tangents,  that  if  these  two  curves  had  intersected 
each  other  in  the  middle,  they  would  have  been  at  right  angles  to  each  other  ; 
they  are,  however,  still  the  projections  of  two  straight  lines  bent  upon  the  cylin- 
dric  surface. 

To  draw  a tangent  to  the  point  n.  Diaw  ?i  4 parallel  to  E A,  meeting  the 
curve  AB  in  4.  Draw’  4 u perpendicular  to  the  radical  line,  and  make  4u  equal 
to  the  development  of  the  arc  4 A.  Draw’  u t perpendicular  to  A G,  and  join 
tn,  which  is  the  tangent  required. 

'Po  find  the  curvature  of  a stone  along  the  two  edges  of  the  longitudinal  joints, 
and  along  the  heading-joints  of  the  intrados.  In  fig.  2,  Plate  X.,  which  is  a 
development  of  the  intrados,  abed  is  the  development  of  ’die  intrados  of  an 
arch-stone;  it  is  required  to  find  the  curvature  along  b and  ad;  also  in  the  di- 
rection ab,  d c,  at  the  ends. 

In  fig.  1,  make  O A equal  to  the  radius  of  the  cylinder,  and ‘through  A draw 
B E perpendicular  to  A O.  Make  the  angle  BOA  equal  to  the  complement  of 
the  angle  with  the  joints  in  the  development  of  the  intrados  made  with  the 
springing-lines,  that  is,  equal  to  the  angle  DA  E,  fig.  2.  Make  O C,fig.  1,  equal 
to  O B,  and  draw  O D perpendicular  to  B C.  Make  O D equal  to  O A.  Then 
with  the  transverse  axis  B C,  and  semi-conjugate  O D,  describe  the  semi-elliptic 
arc  or  curve  C D B ; then  the  portion  of  the  elliptic  arc  on  each  side  of  the  point 
D will  be  the  curvature  in  fiig.  2,  along  the  longitudinal  edge  be  or  da  of  the 
sofiit  of  a stone. 

Again,  produce  D O to  E,  and  make  OE  equal  to  OD.  In  OB,  take  O G, 
equal  to  O A,  the  radius  of  the  circular  end  of  the  cylinder;  then  with  the  trans- 
verse axis  D E,  and  the  semi-conjugate  O G,  describe  the  semi-elliptic  arc  D G E, 
and  the  small  portion  of  this  arc  on  each  side  of  the  point  G has  the  same  curva- 
ture ns  a b or  d e,  fig.  2.  Therefore  the  stone  being  w’rought  hollow^  as  directed 
in  the  description  of  the  preceding  plate,  then  the  mould  shown  at  D is  that  for 
working  the  longitudinal  joints,  or  those  which  terminate  on  the  soffit  in  the  lines 
ad  and  be.  In  like  manner,  the  mould  G is  that  for  working  the  heading-joints 
which  terminate  upon  the  soffit  in  the  lines  ab,  de,  &lc.  It  will  hardly  be  neces- 


Sr. 


ft" 


- 


V T ^ ^ -1 

‘i  ' ■ , 

' V 


) 


> 

'■SSi 


1 


I 


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/ 


r 


ON  OBLIQUE  AKCHES. 


125 


sary  to  remind  the  reader,  that  the  convex  edge  of  the  squares  at  D and  G 
is  to  be  applied  upon  the  hollow  soffit  already  wrought.  The  curvature  of 
these  moulds  may  be  shown  by  calculation  thus : let  R be  the  radius  of 
curvature,  a = the  semi-transverse  axis,  and  h = the  semi-conjugate  ; then 
6 : rt  : : a : R = 

6 

As,  for  example  to  this  formula,  let  the  radius  of  the  cylindric  intrados,  or  b = 
13  feet,  and  the  semi-transverse  axis,  or  a = 28  feet. 

28 

28 

224 

56 

13)784(60  feet  4 inches  nearly 
78 

4 

12 

To  find  the  angle  of  the  joints  of  the  face  of  the  arch,  and  intrados  of  the 
oblique  arch  with  spiral  joints. 

Let  the  semicircular  arc  ABC,  Fig.  4,  be  a section  of  the  intrados  at  right 
angles  to  the  axis  of  the  cylinder.  Draw  C D and  A E perpendicular  to  the 
diameter  A C.  Draw  A D,  making  an  angle  with  C D,  equal  to  the  inclination 
which  the  plane  of  the  face  of  the  arch  makes  with  the  vertical  plane  which  is 
parallel  to  the  axis  of  the  cylinder,  and  which  passes  through  the  springing-line 
of  the  arch. 

Find  the  edge  D/G  of  the  development  and  face  of  the  arch,  or  draw  the 
curve  D/G  with  a mould  made  from  the  development  before  shown.  Draw 
the  face  of  the  ring-stones  AKD.  Let  it  now  be  required  to  find  the  fourth 
from  the  point  D.  IMake  D / equal  to  the  portion  D 4 of  the  intrados  AKD. 
Draw//,  the  development  of  a part  of  the  longitudinal  spiral  joint  corresponding 
to  the  point  4 of  the  elliptic  arc  AKD.  Draw  the  line  « / a tangent  to  the  curve  at 
/.  To  do  this,  we  shall  again  repeat  the  process  of  which  the  principle  has  already 
been  taught,  namely:  — On  C D,  as  a diameter,  describe  the  semicircle  C^D 
and  draw / q,  intersecting  C D perpendicularly.  Draw  a tangent  to  the  semi- 
circular arc  at  the  point  q,  and  make  qu  equal  to  the  development  of  the  portion 

D of  the  semicircular  arc.  Draw  u t perpendicular  to  C D,  meeting  C D,  or 
C D produced  in  the  point  /.  Through  / draw  the  straight  line  /f,  and  t s will  be 
a tangent  to  the  curve  at  the  point.  By  this  means  we  have  the  angles  which 
the  spiral  joints  in  the  intrados  make  at  the  point  4 with  the  elliptic  curve 
AKD. 

To  find  the  angle  made  by  the  normal  and  the  curve,  in  fig.  4. 


126 


PRACTICAL  MASONRY. 


In  fig.  7,  draw  the  straight  line  ab,  and  make  ab  equal  to  the  radius  of  curva- 
ture of  the  elliptic  arc  A K D at  the  point  4.  This  radius  would  be  near  enough 
to  make  it  the  half  of  the  half  sum  of  the  semi-parameters  of  the  two  axes. 

But  if  greater  nicety  is  required,  let  the  radius  of  curvature  be  denoted  by  ii, 
the  semi-transverse  axis  O D or  O A be  denoted  by  a,  and  the  semi-conjugate, 
which  is  the  radius  of  the  semi-circular  arc  ABC,  be  denoted  by  b,  and  Jet  the 
distance  Op  be  denoted  by  x ; then  will  r—  ; which  will  be  exact 

to  the  number  of  figures  found  in  the  operation  here  indicated. 

Having  thus  found  the  radius  of  curvature,  either  mechanically  or  by  calcula- 
tion, make  ab,  fig.  7,  equal  to  that  radius.  From  the  point  a as  a centre,  with 
the  distance  a b,  describe  the  arc  be  ; and  draw  the  straight  line  b d a.  tangent  to 
the  curve. 

To  find  the  angle  made  by  a tangent  plane  to  the  cylindric  surface  at  the 
point  4,  fig.  4,  and  the  plane  of  the  face  of  the  arch. 

Draw  the  straight  line  4ua  tangent  to  the  elliptic  curve  A K D at  the  point  4, 
and  draw  4 v parallel  to  AD.  Transfer  the  angle  u 4v  io  a be,  fig.  5. 

In  fig.  5,  at  the  point  b,  in  the  straight  line  b e,  make  the  angle  eb  d equal  to 
the  angle  D O P,  fig.  3,  which  the  axis  makes  with  the  plane  of  the  face  of  the 
arch.  Again,  in  fig.  5,  draw  ef  perpendicular  to  a b,  intersecting  a i in  the  point 
a.  Draw  e d perpendicular  to  e b,  and  e e perpendicular  to  e f.  IMake  e e equal 
to  e d,  and  join  e a;  then  will  the  angle  e af  be  the  inclination  of  the  curved 
surface  of  the  cylindric  intrados  and  the  face  of  the  ring-stones. 

We  have  now  ascertained  two  sides,  and  the  contained  angle  of  the  trehedral ; 
in  order  to  find  the  remaining  parts,  the  third  side  of  this  trehedral  is  the  angle  of 
the  joints  of  the  intrados  and  face  of  the  arch,  by  applying  the  proper  curved 
moulds  to  the  angular  point ; it  is,  however,  rather  unfavorable  to  our  purpose, 
that  the  angle  a b d.  Jig.  7,  is  a right  angle,  and  that  the  angles  I ft  and  Ifs,  fig. 
4,  differ  but  in  a very  small  degree  from  right  angles.  As  from  this  circum- 
stance the  principle  cannot  be  made  evident,  we  shall  therefore  suppose,  that 
these  angles  have  at  least  a certain  degree  of  obliquity. 

In  Jigs.  3 and  5,  let  A B C equal  to  angle  I fit,  fig.  4,  and  A B D,  Jigs.  3 and  6, 
equal  to  the  angle  abd,fig.  7 ; thus,  in  figs.  3 and  6,  draw  D e,  intersecting  A B 
in  /,  or  producing  D c to  meet  A B in  /.  At  the  point  /in  the  straight  line  <?/in 
Jig.  6,  make  the  angle  ef  g equal  to  the  angle  e ae,  fig.  5 ; or,  in  fig.  3,  make  the 
angle  e f g equal  to  the  supplement  of  the  angle  e af.  In  figs.  3 and  6,  dmw  e k 
perpendicular  to  B C,  B C in  i,  or  B C produced  in  i.  Draw  eg  perpendicular 
to  e f and  e h to  e C.  Make  e h equal  to  e g,  and  join  h i.  Make  i K equal  to 
i h,  and  join  B K ; then  will  the  angle  C B K be  the  angle  of  the  joints  of  the  in- 
trados and  face  of  the  arch. 


•*> 


1 


i 


I 


i 


N 


V 


9 


T 


A R r 1^1  K 


A CIECULAR  ARCH  IN  A CIRCULAR  WALL. 


127 


When  each  of  the  given  sides  is  a right  angle,  then  the  remaining  side  of  the 
trehedral  will  be  the  same  as  the  contained  angle  ; that  is,  the  angle  of  the  joints 
of  the  intrados  and  face  of  the  arch  will  be  the  same  as  the  angle  e af  Jig.  5. 
In  this  case,  no  lines  are  necessary  in  order  to  discover  the  angle  of  the  joints. 

In  order  to  apply  the  angle  C B K,  one  of  the  lines  which  applies  to  the  face 
must  be  straight,  and  the  curved  edge  shown  by  the  bevel  at  D of  the  preceding 
plate  must  be  so  applied,  that  the  other  leg  of  the  bevel  may  be  a tangent  to  the 
curve  at  the  angular  point  B,  and  this  will  complete  what  is  necessary  in  the 
construction  of  an  oblique  arch  with  spiral  joints. 


SECTION  VII.  — A Circular  Arch  in  a Circular  Wall. 

PROBLEM  I. 

To  execute  a semi-cylindric  arch  in  a cylindric  wall,  supposing  the  axes  of  the 
two  cylinders  to  intersect  each  other.  Given  the  two  diameters  of  the  wall,  and 
the  diameter  of  the  cylindric  arch,  and  the  number  of  arch-stones. 

Fig.  1,  Plate  IX.  From  any  point  b,  w ith  the  radius  of  the  inner  circle  of  the 
wall,  describe  the  circle  A B C,  or  as  much  of  it  as  may  be  necessary  ; and  from 
the  same  point  o,  wdth  the  radius  of  the  exterior  face  of  the  w'all,  describe  the  cir- 
cle D E F,  or  as  much  of  it  as  may  be  found  convenient. 

Apply  the  chord  AB  equal  to  the  width  of  the  arch,  and  draw  DA  and  E B 
perpendicular  to  AB  or  DE;  then  ABDE  will  be  the  plan  of  the  cylindric 
arch. 

Draw  Op  perpendicular  to  A B,  and  draw  t v perpendicular  to  Op.  From 
the  point  p as  a centre,  with  the  radius  of  the  intrados  of  the  arch,  describe  the 
semicircular  arc  q7's;  and  from  the  same  point  p,  with  the  radius  of  the  extra- 
dos,  describe  the  semicircular  arc  t u v.  Divide  the  arc  qrs  into  as  many  equal 
parts  as  the  arch-stones  are  intended  to  be  in  number,  that  is,  here  into  nine  equal 
parts.  From  the  centre  p,  draw  lines  through  the  points  of  division  to  meet  the 
curve  tuv;  and  these  lines  will  be  the  elevation  of  the  joints ; and  the  joints, 
together  with  the  intradosal  and  extradosal  arcs,  will  complete  the  elevation  of 
the  arch. 

Find  the  development.  Jig.  2,  as  in  Jig.  9,  Plate  IV.,  and  the  parallel  equi- 
distant lines  to  the  same  number  as  the  joints  in  the  elevation  will  be  the  joints  of 
the  .soffits  of  the  stones;  and  the  surfaces  comprehended  by  the  parallel  lines 
and  the  edges  of  the  developments  will  be  the  moulds  for  shaping  the  soffits  of 
the  stones. 


128 


PRACTICAL  MASONRY. 


In  jig.  3.  Let  A B be  equal  to  the  diameter  of  the  external  c}dinder.  Draw 
A C and  B D each  perpendicular  to  A B.  Bisect  A B in  p,  from  which  describe 
the  intradosal  and  extradosal  arcs,  and  draw  the  joints  as  in  jig.  1.  Produce  the 
joints  to  meet  A C or  B D,  in  the  points  e,f,  g,  Slc.  ; then  it  is  evident  that,  since 
every  section  of  a cylinder  is  an  ellipse,  the  lines  p A,  p e,  pf,  p g,  &c.,  are  the 
semi-transverse  axes  of  the  curves  which  form  the  joints  in  the  face  of  the  arch, 
and  that  these  curves  have  a common  semi-conjugate  axis  equal  to  half  the 
diameter  of  the  cylinder. 

Therefore,  upon  any  indefinite  straight  line  p Q,  jig.  4,  set  off  the  semi-axis 
p A,  p e,  p f p g,  &.C.,  and  draw  p B perpendicular  to  p Q.  From  p,  with  the 
radius  p A,  describe  an  arc  A B.  On  the  semi-axes  p e and  p B,  describe  the 
quadrantal  curve  of  an  ellipse  ; in  the  same  manner  describe  the  quadrantal 
curves /B,  gB,  &,c.  Make  p q equal  to  p q,jig.  3,  and  in  jig.  4 draw  q t paral- 
lel to  p B,  intersect  the  curves  A B,  e B, /B,  &lc.,  in  the  points  i,  k,  I,  &,c. ; then 
h i m,  h k n,  h I o,  &.C.,  are  the  bevels  to  be  applied  in  forming  the  angles  of  the 
joints ; namely,  the  bevel  h i m is  that  of  the  impost,  the  straight  side  h i being 
applied  upon  the  soffit  or  intrados,  and  the  curved  part  i m horizontally  to  the 
curve  of  the  exterior  side  of  the  wall ; the  point  /i,  of  the  bevel  h k n,  jig.  4,  applies 
to  the  point  k,  jig.  3,  so  that  k h may  coincide  with  the  joint  upon  the  intrados, 
and  the  curved  edge  kn,fig.  4,  upon  the  face  k n,fig.  3 ; and  so  on. 

As  to  the  angles  which  the  beds  of  the  stones  make  with  the  intrados,  they  are 
all  equal,  and  may  be  found  from  the  elevation  s v y x,fig.  1 ; w'hich  is  the  same 
as  a section  of  one  of  the  arch-stones  perpendicular  to  any  one  of  the  joints 
on  the  soffits. 

The  faces  of  the  stones  must  be  wrought  by  a straight  edge,  by  perpendicular 
lines.  'Phe  first  thing  to  be  done  is  to  work  one  of  the  beds ; secondly,  work  the 
intrados,  — at  first  as  a plane  surface  at  an  angle  s x y,  or  x s v,jig.  1 ; then  gauge 
off  the  bed  of  the  soffit,  and  work  the  other  bed  of  the  stone  by  the  angle  v s x or 
y X s ; then  apply  the  proper  soffit,  1 , 2,  or  3,  jig.  2 ; and  lastly,  the  two  moulds 
in  jig.  4. 


SECTION  VIII.  — A Coxic  Arch  in  a Cylindric  Wall. 

PROBLEM  I. 

To  execute  a semi-conic  arch  in  a cylindric  wall,  supposing  the  vertex  of  the 
cone  to  meet  the  axis  of  the  cylinder.  Given  the  interior  and  exterior  diameters 
of  the  wall,  the  length  of  the  axis  of  the  cone,  and  the  diameter  of  its  base. 


TI)  FUS'JD)  TTI  K J5F  g'iPOITiE 


r/  lo. 


ir.irnnsiii,  jv 


n n. 


MI  GMT  SMGTI(M  MM  MILAM  E 


L, 


nr  ir  mison  xr 


12. 


I'm'TinijAm  I'^rAJLTLi 


w.wirnsow  jv 


A CONIC  ARCH  IN  A CYLINDRIC  WALL. 


129 


Example  I.  — From  the  point  O,  fig.  1,  Plate  XII.,  with  the  radius  of  the  in- 
terior surface  of  the  wall,  describe  the  arc  ABC,  and  from  the  same  point  O,  with 
the  radius  of  the  exterior  surface,  describe  the  arc  D E F,  and  the  area  between 
the  arcs  ABC  and  D E F will  contain  the  plan  of  the  wall. 

Draw  any  line  O p,  and  make  O p equal  to  the  length  of  the  axis  of  the  cone. 
Through  p draw  tv  perpendicular  to  Op.  From  p as  s.  centre,  with  the  radius 
of  the  base  of  the  cone,  describe  the  semicircle  qr  s meeting  ^ in  the  points  q 
and  s.  Divide  the  arc  q rs  into  as  many  equal  parts  as  the  arch-stones  are  to 
be  in  number,  that  is,  in  this  example,  into  nine  equal  parts.  Through  the  points 
of  division  draw  the  joint  lines,  which  will  of  course  radiate  from  the  centre  p. 
The  extradosal  line  tuv  is  here  described,  as  we  here  suppose  the  cone  to  be  of 
an  equal  thickness,  and  consequently  the  axis  of  the  exterior  cone  longer  than 
that  of  the  interior. 

From  the  points  1,  2,  3,  &c.,  where  the  lower  ends  of  the  joints  of  the  arch- 
stones meet  the  intradosal  arc,  draw  lines  perpendicular  to  t v,  meeting  t v in  the 
points  I,  A:,  I,  m,  &,c.  From  these  points  draw  lines  to  the  vertex  of  the  cone  at 
O, meeting  the  arc  D E,  or  plan  of  the  wall  under  the  arch,  in  the  points  a,b,c,  d, 
&c.  Draw  the  lines  a e,  bfy  c g,  d h,  &c.,  parallel  to  the  chord  D E,  to  meet  op 
in  IV.  In  fig.  2,  draw  the  straight  line  A B,  in  which  take  the  point  p near  the 
middle  of  it,  and  make  p A,  p B,  each  equal  to  the  radius  of  the  exterior  surface 
of  the  cylindric  wall.  Through  the  points  A and  B draw  f g,  f g,  perpendicu- 
lar to  A B. 

From  the  point  p as  a centre,  with  any  radius,  describe  a semicircular  arc,  and 
divide  it  into  nine  equal  parts  as  before.  Through  the  points  of  division  draw 
the  radiating  lines  to  meet  f g in  the  points  c,/,  g,  &.c.  From  fig.  1 transfer  the 
distances  E to,  ae,bf,  eg,  &,c.,  fig.  1,  to  p g',  fig.  2,  p r,  ps,  p t,  &lc.,  on  each  side 
of  the  point  p.  Draw  the  perpendiculars  rk,  s I,  t m,  &lc.,  to  A B,  which  will  in- 
tersect with  the  radials  p e,  pf,  p g,  &c.,  in  the  points  k,  /,  m,  &c. ; through  the 
points  k,  /,  m,  &,c.,  on  each  side,  draw  a curve,  and  this  curve  will  be  the  eleva- 
tion of  the  intrados  of  the  arch. 

Fig.  3 exhibits  another  method  by  which  the  heights  of  the  points  k,  /,  m,fig.  2, 
might  have  been  found.  This  method  is  as  follows : — Upon  a straight  line 
a b,  and  from  the  point  a,  make  a b\  a c,  a d,  a e,  &c.,  and  a fi  respectively  equal 
to  O i,  O k,  O /,  &LC.,fig.  1.  In  fig.  3,  draw  the  straight  lines  b g,  ch,  d i,  e k,fo, 
perpendicular  to  a b.  Make  bg,ch,  c?  i,  e A:,  respectively  equal  to  the  heights 
il,  k2,  13,  m4.  Draw  the  straight  lines  ag,  a h,  a i,  a k,  intersecting  f o in  the 
points  I,  m,  n,  o. 

In  fig.  2,  make  r k,  s I,  tm,un,  respectively  equal  to  fl,fm,fn,fo,fig.  2, 
and  thus  the  points  k,  I,  m,  &c.,  are  found  by  a different  method,  which  is  more 

17 


132 


PRACTICAL  MASONRY. 


It  will  be  necessary  to  work  the  arch-stones  into  prisms,  of  which  the  ends  are 
the  sections  of  the  stones  in  the  right  section  of  the  arch,  namely,  the  same  as 
the  compartments  adjacent  to  the  curve  in  the  elevation.  The  prisms  being 
formed,  draw  the  figure  of  the  soffit  of  the  stone  upon  the  surface  intended  for 
the  same.  Then  apply  the  joint-mould  upon  each  face  of  the  stone  intended  for 
the  joint,  and  draw  the  figure  of  the  joints  ; then  reduce  the  end  of  the  stone 
which  is  to  form  a part  of  the  face  of  the  arch  in  such  a manner  that  when  the 
arch-stone  is  placed  in  the  position  which  it  is  to  occupy,  or  in  a similar  situation, 
a straight  edge,  applied  in  a horizontal  position,  may  have  all  its  points  in  contact 
with  the  surface  of  the  face  of  the  stone  now  formed.  The  face  being  thus 
formed,  the  conic  surface  must  also  be  formed  by  means  of  a straight  edge,  in 
such  a manner  that  all  points  of  the  straight  edge  must  coincide  with  the  sur- 
face when  the  straight  edge  is  directed  to  the  centre  of  the  cone. 


SECTION  IX.  — Construction  of  the  Moulds  for  Spherical  Niches,  both  with  Radiat- 
ing AND  Horizontal  Joints,  in  Straight  Walls. 

Whex  niches  are  small,  the  spherical  heads  are  generally  constructed  with  ra- 
diating joints  meeting  in  a straight  line  which  passes  through  the  centre  of  the 
sphere  perpendicularly  to  the  surface  of  the  wall,  when  the  w^all  is  straight ; but 
when  it  is  erected  upon  a circular  plan,  the  line  of  common  intersection  of  all  the 
planes  of  the  joints  is  a horizontal  line  tending  to  the  axis  of  the  cylindric  wall. 

Niches  of  large  dimensions  will  be  more  conveniently  constructed  in  horizontal 
courses,  than  with  joints  which  meet  in  the  centre  of  the  spheric  head ; since,  in 
the  latter,  the  length  and  breadth  of  the  stones  are  always  proportional  to  the  di- 
ameter or  radius  of  the  sphere,  and  therefore,  when  the  diameter  is  great,  the 
stones  w'ould  be  difficult  to  procure. 

I’he  construction  of  niches  depends  also  upon  the  nature  and  position  of  the 
surface  from  which  they  are  recessed ; namely,  a spherical  niche  may  be  made 
in  a straight  wall,  either  vertical  or  inclined ; or  it  may  be  constructed  in  a circu- 
lar wall  or  a spherical  surface,  such  as  a dome. 

This  subject,  therefore,  naturally  divides  itself  under  several  heads  or  branch- 
es ; the  principal  are,  a spherical  niche  in  a straight  wall,  with  radiating  joints ; a 
spherical  niche  in  a straight  wall,  in  horizontal  courses ; a spherical  niche  in  a 
circular  wall,  with  radiating  joints ; a spherical  niche  in  a circular  wall,  in  hori- 
zontal courses ; and  a spherical  niche  in  a spherical  surface  or  dome. 


\ 

I 


. r f, 


'4 


/ . 


V-'  ■ A- 


l^l  13. 


K!  Ij  K!V.VT''IL)^  IDKA  llj)'li)©3:{  Y a 


/ Mi/ir 


h r-* 

r ^ 

" 

NICHES,  WITH  RADIATING  JOINTS. 


133 


SECTION  X. — Examples  of  Niches,  with  Radiating  Joints  in  Straight  Walls,  as  in 

Plate  XIII.,  Fig.  1. 

XicHES  of  very  small  dimensions  will  be  easily  constructed  in  two  equal  cubic- 
al stones,  hollowed  out  to  the  spherical  surface,  with  one  vertical  joint ; the  por- 
tion of  the  spherical  surface  formed  by  both  stones  being  one  fourth  of  the  entire 
surface  of  the  sphere. 

Fig.  '2  is  the  elevation,  fig.  3 the  plan,  and  fig.  4 the  vei'tical  section  perpen- 
dicular to  the  face  of  the  straight  wall  of  such  a niche. 

The  first  operation  is  to  square  the  stone ; namely,  to  bring  the  head  of  each 
stone  to  a plane  surface,  then  the  vertical  Joints  and  the  upper  and  lower  beds  to 
plane  surfaces  at  right  angles  with  the  surface  which  forms  the  head. 

The  two  stones  as  hollowed  out  are  shown  at  Xos.  3 and  4.  To  show  how 
they  are  wrought,  we  will  commence  with  one  of  the  stones  after  being  brought 
to  the  cubical  form.  Let  this  stone  be  No.  3.  In  the  solid  angle  of  the  stone 
formed  by  the  head,  the  vertical  joint  and  the  lower  bed  meeting  in  the  point  p, 
apply  the  quadrantal  mould,  Xo.  2,  upon  each  side,  so  that  the  angular  point  of 
the  two  radiants  may  coincide  with  the  point  p,  and  one  of  the  radiants  upon  the 
arris  of  the  stone  which  joins  the  point  p ; then  if  the  face  of  the  quadrantal  mould 
coincide  with  the  surface  of  the  stone,  the  other  radiant  line  will  also  coincide, 
because  the  angle  of  the  mould  and  all  the  angles  of  the  faces  of  the  stone  are 
right  angles. 

By  this  means  we  obtain,  by  drawing  round  the  curved  edge  of  the  mould,  the 
three  quadrantal  arcs  ah  c,  a g h,  and  c i Ji.  The  superfluous  stone  being  cut 
away,  the  spherical  surface  will  be  formed  by  trial  of  the  mould,  Xo.  2. 

Fig.  1,  Plate  XIV.,  is  the  elevation,  and /?«•.  2 the  plan,  of  a niche  in  a straight 
wall. 

The  elevation,  1,  not  only  shows  the  number  of  stones  which  must  be  odd, 
and  the  number  of  radiating  joints,  which  must  in  consequence  be  one  less  than 
the  number  of  stones,  but  also  the  thickness  of  these  stones,  and  the  moulds  for 
forming  the  heads  and  opposite  sides. 

The  head  of  the  niche  being  spherical,  makes  it  a surface  of  revolution.  It 
follows,  therefore,  that  the  sections  through  the  joints  are  equal  and  similar  figures  ; 
hence,  if  all  the  joints  were  of  one  length,  one  mould  would  be  sufficient  for  the 
whole ; but  since,  in  this  example,  they  are  of  different  lengths,  every  two  joint- 
moulds  will  have  a common  part ; and  thus  if  the  mould  for  the  longest  joint  be 
found,  each  of  the  other  moulds  will  only  be  a part  of  the  mould  thus  found. 

In  order  to  ascertain  the  mould  for  each  joint,  the  longest  being  AD,  fig.  1, 


134 


PRACTICAL  MASONRY. 


extending  from  the  centre  to  the  extremity  of  the  stone  upon  one  side  of  the 
plan,  the  next  longest  is  A F,  extending  from  the  centre  to  the  extremity  of  the 
keystone,  and  the  shortest  A G. 

Upon  P 1,  make  A F equal  to  A F^^,  and  A G equal  to  A G'.  Perpen- 

dicular to  P Q draw  D d,  Ff,Gg,  meeting  the  front  line  R S of  the  plan,  fig.  2, 
in  the  points  d,f  g^  intersecting  the  back  line  of  the  stone  in  the  points  m,  n,  o ; 
then  will  No.  1,  hike  dm,  be  the  mould  for  the  first  stone  raised  upon  the  plan, 
hikefn  the  mould  for  the  joint  on  each  side  of  the  keystone, /if the 
mould  for  the  first  stone  above  the  springing-line.  These  moulds  are  shown 
separately  at  I.,  II.,  III.,  and  identified  by  similar  letters. 

Nos.  1,2,3,  exhibit  the  first,  second,  and  third  stones  of  the  niche  as  if 
wrought  to  the  form  of  the  spherical  surface ; No.  3 being  the  keystone  ; there- 
fore the  two  remaining  stones  are  wrought  in  a reverse  order  to  the  stones  ex- 
hibited at  No.  1 and  No.  2. 

The  first  part  of  the  operation  is  to  work  the  stones  into  a wedge-like  form,  so 
that  the  right  section  of  these  stones  may  correspond  to  the  figures  formed  by 
the  radiations  of  the  joints  to  the  centre  A,fg.  1,  and  by  the  horizontal  and  ver- 
tical joints  of  the  stones  adjacent  to  those  which  form  the  niche ; for  this  pur- 
pose, two  moulds  for  each  head  will  be  necessary,  namely,  one  whole  mould  must 
be  made  for  each  stone,  and  one  mould  for  the  part  .within  the  circle,  which  will 
apply  to  every  stone,  in  order  to  form  the  extent  of  the  part  within  the  recess  ; 
thus  a mould  formed  to  the  sectoral  frustrum  E E' K' K in  the  elevation,  fig  1, 
will  apply  alike  to  all  stones,  as  will  be  shown  presently. 

The  next  thing  is  to  form  the  moulds  K'  K D S G^,  K''  K'  G^  T F'',  and 
K"  K''  F''  F^'',  of  the  heads  ; the  application  of  these  moulds  is  as  follows  : — 

Having  wrought  the  under  bed,  the  head  and  back  of  each  stone,  and  having 
formed  a draught  next  to  the  edge  of  the  bed,  upon  the  side  which  is  to  lie  upon 
the  cylindric  part  in  the  centre,  at  a right  angle  with  the  head,  apply  the  mould 
K''  K D S G',  fig.  1,  upon  the  head  of  the  stone  No.  1,  so  that  the  straight  edge 
K D may  be  close  upon  the  bed  of  the  stone,  and  draw  by  the  other  edges  of 
the  mould  thus  applied  the  figure  r'rdsg;  and,  in  the  same  line  rd,  close  to 
the  bed,  apply  the  mould  K'  K E E',  fig.  1 , and  by  the  other  edges  of  this  mould 
draw  the  figure  rV  e c'.  Appl}'  the  mould  K'  K D S G'  to  the  opposite  or  paral- 
lel side  of  the  stone,  close  to  the  bed,  and  draw  a similar  and  equal  figure  as 
was  done  by  the  same  mould  when  it  was  applied  to  the  head  ; this  done,  work 
the  upper  bed  of  the  stone. 

Proceed  in  like  manner  with  the  stones  exhibited  at  No.  2 and  No.  3,  and  sim- 
ilarly with  the  stones  on  the  left-hand  side  of  the  arch ; the  stones  No.  1 and 
No.  2 answering  to  those  on  the  right  hand  of  the  keystone. 


ir,  ir.  m/*or>  S'r. 


ri  u<. 


Fu!  . } 


c II  ws 


Fiq  1. 


I 


/Y,  16 . 


fWWiWVson  SiC. 


NICHES  IN  STRAIGHT  WALLS. 


135 


In  order  to  show  the  application  of  the  moulds  marked  I.,  IL,  III.,  at  the  bottom 
of  the  plate,  taken  from  the  plan, /g-.  2;  the  mould  I.  applies  to  the  under  bed 
of  the  stone  No.  1 ; the  next  mould  II.  applies  upon  the  upper  bed  of  No.  1, 
and  upon  the  under  bed  of  No.  2 ; and  the  mould  III.  applies  upon  the  upper 
bed  of  No.  2,  and  upon  each  side  of  the  keystone.  No.  3. 

As  every  arch  has  both  a right  and  left  hand  side,  and  as  every  joint  is  formed 
by  the  surfaces  of  two  stones,  every  mould  has  four  applications,  one  on  each  of 
the  four  stones. 

In  order  to  render  these  applications  of  the  moulds  I.,  II.,  III.,  as  clear  as  possi- 
ble, the  corresponding  situations  of  the  points  marked  upon  each  stone  by  each 
respective  mould  are  marked  by  similar  letters  to  those  on  the  moulds  I.,  II.,  III., 
or  their  correspondents  on  the  plan,  2;  namely,  on  the  under  bed  of  the 
stone  No.  1 will  be  found  the  letters  h,  i,  k,  e d,  m,  as  in  the  mould  I. ; upon  the 
under  bed  of  No.  2 will  be  found  h\  i',  k',  e',  g,  o' ; as  also  upon  the  upper  bed 
of  No.  1,  i',k',  e,' g',  and  upon  the  right-hand  side  of  the  keystone,  No.  3,  will  be 
found  the  letters  h",  i",  k”,  e",/",  n",  as  also  similar  letters  upon  the  upper  bed. 
No.  2,  to  those  of  the  mould  III. 

ARCH,  WITH  SPLAYED  JAMBS. 

To  find  the  angles  of  the  joints  formed  by  the  front  and  intrados  of  an  ellipti- 
cal arch,  erected  on  splayed  jambs. 

No.  1,  on  fg.  3,  is  the  place  of  the  impost;  No.  2,  the  elevation. 

The  impost  A'B'C'D'E  is  the  first  bed  ; fghik,  the  second  ; Imnop,  the 
third  ; qrstii,  the  fourth ; vwxyz,  the  fifth.  The  other  beds  are  the  same  in 
reverse  order.  The  breadth  of  all  these  beds  is  the  same  as  that  of  the  arch 
itself.  The  lengths  k K,  n P,  s U,  a:  Z,  of  the  front  lines  of  the  moulds  of  the 
beds  are  respectively  equal  to  the  lines  H F,  N L,  S Q,  X V,  on  the  face  of  the 
arch.  And  also,  hg,  nm,  s r,  x tc,  on  the  parts  of  the  moulds  equal  to  the  cor- 
responding distances  H C,  N M,  S K,  X W,  on  the  face  of  the  arch.  The  dis- 
tances kf,  pi,  ug,  rv,  are  equal  to  the  perpendicular  part  AE  of  the  impost. 

SECTION  XI.  — Examples  of  Niches  in  Straight  Walls  with  Horizontal  Courses,  as 

IN  Plate  XIV.,  Fig.  1. 

Let  Jig.  2 represent  a niche  with  horizontal  courses.  No.  1 being  the  elevation 
exhibiting  three  arch-stones  on  each  side  of  the  keystone,  and  No.  2 the 
plan,  consisting  of  two  stones,  making  together  a semicircle,  each  being  one 
quadrant. 

The  heads  of  the  stones  in  the  wall,  on  the  right-hand  side  of  the  arch,  which 


136 


PRACTICAL  MASONRY. 


also  form  a portion  of  the  concave  surface,  are  ABODE,  FDCGH  M, 
M G K L M,  and  the  keystone  L K K L.  Round  each  of  these  figures  circum- 
scribe a rectangle,  so  that  two  sides  may  be  parallel  and  two  perpendicular  to 
the  horizon  ; thus,  round  the  head  of  the  stone  ABODE  circumscribe  the 
rectangle  A N O E';  round  the  figure  F D 0 G M I,  the  head  of  the  second  stone, 
circumscribe  the  rectangle  P Q R I,  &,c. 

Draw  the  straight  lines  am  and  ai,fig.  3,  No.  1,  forming  a right  angle  with 
each  other ; from  the  point  a as  a centre,  with  the  radius  dbc,  describe  the  arc 
c c,  meeting  the  lines  a m and  a i in  the  points  c,  c. 

Let  the  quadrangular  figure  hgfe,^o.  1,  be  considered  as  the  upper  bed 
of  a stone,  which,  as  well  as  the  lower  bed,  is  wrought  smooth,  these  two  sur- 
faces being  parallel  planes  at  a distance  from  each  other  equal  to  the  line  A E 
or  CT),fig.2.  Moreover,  let  mcc'bbdd  be  considered  as  a mould  made  to 
the  figure  before  described  and  laid  flat  on  the  upper  bed  of  the  stone  in  its  true 
position,  the  points  c,  c,  of  the  mould  being  brought  as  near  to  the  side  A e as 
will  just  leave  a sufficient  quantity  of  stone,  in  order  to  work  it  complete.  By 
the  edges  of  the  mould  thus  placed,  draw  the  curve  cc,  the  straight  lines  cm 
and  c i,  and  the  rough  edges  ik  and  ml. 

Perpendicular  to  the  upper  bed,  and  along  the  arc  cc\  cut  the  stone  so  as  to 
form  a surface  perpendicular  to  the  upper  bed,  and  the  surface  thus  formed  will 
necessarily  be  cylindric  ; through  each  of  the  straight  lines  cm  and  c'l  cut  a 
surface  perpendicular  to  the  said  upper  bed,  and  these  surfaces  will  be  the 
planes  of  the  vertical  joints,  and  will  be  at  a right  angle  with  each  other;  then 
with  a gauge,  of  which  the  head  is  made  to  the  cylindric  surface,  and  which  is 
set  to  the  distance  OD,  //^.  2,  No.  1,  draw  the  curve  line  dd  on  the  upper  bed 
of  the  stone.  Upon  the  lower  bed  of  the  stone,  with  the  gauge  set  to  the  dis- 
tance N B,  draw  the  arc  b b\ 

The  thickness  of  the  stone  is  exhibited  at  No.  '2,  fig.  3,  the  upper  bed  being 
represented  by  the  line  n r,  and  the  lower  bed  by  the  line  q u,  so  that  n r and 
</ « are  parallel  lines,  the  distance  between  them  being  equal  to  the  thickness 
of  the  stone,  namely,  equal  to  A E,  fig.  2,  No.  1 . Lastly,  with  a plane  or  com- 
mon gauge  set  to  the  distance  N C,fig.  2,  No.  1,  draw  the  line  c c on  the  cylin- 
dric surface,/^.  3,  No.  1. 

Now,  in  fig.  3,  the  line  d d\  No.  2,  represents  the  arc  d d'.  No.  1 ; c c\  No.  2, 
represents  the  arc  c c',  No.  1 ; and  b b\  No.  2,  represents  the  arc  b 6,  No.  1 ; so 
that  the  stone  must  be  cut  away  between  the  line  d d'  on  the  upper  bed,  and 
c c on  the  cylindric  surface,  by  means  of  a straight  edge,  so  as  to  form  a conic 
surface  ; this  may  be  done  by  setting  a bevel  to  the  angle  E D C,fig.  2,  No.  1. 
The  conic  surface  thus  formed  will  be  one  side  of  the  joint  within  the  spheric 
surface. 


/V  I O'. 


JB  M 


4 


PI  17. 


fV  M'  Uihon  .vV. 


CONSTRUCTION  OF  THE  MOULDS. 


137 


Again,  cut  away  the  stone  between  the  line  c c on  the  cylindric  surface  and 
the  arc  h b'  before  drawn  on  the  lower  bed  by  means  of  the  curved  bevel  shown 
at  A,  Jig.  2,  No.  2,  so  as  to  form  a spherical  surface.  This  may  be  done  in  the 
most  complete  manner  by  applying  the  straight  side  of  the  curved  bevel  B,Jig. 
2,  No.  2,  to  the  under  bed  of  the  stone,  so  as  to  be  perpendicular  to  the  curve ; 
then,  if  the  curved  edge  coincide  at  all  points,  the  surface  between  these  lines 
will  be  spherical,  and  will  form  that  portion  of  the  head  of  the  niche  which  is 
contained  on  the  stone. 

In  the  same  manner  all  the  other  stones  may  be  cut  to  the  form  required. 

Fig.  4 exhibits  the  stone  in  the  middle  of  the  second  course,  and  Jig.  5 the 
stone  on  the  left  of  the  same  course  in  the  angle,  which  last  stone  is  one  half  of 
the  stone  represented  by^^.  4. 

Fig.  6 exhibits  the  left-hand  stone  of  the  third  course,  and  Jig.  7 the  keystone, 
which  is  wrought  into  the  frustrum  of  a cone  to  a given  height,  in  order  to  agree 
with  the  circular  courses ; and  to  prevent  any  tendency  of  the  keystone  from 
coming  out  of  its  place,  the  upper  part  is  cut  into  the  frustrum  of  a pyramid. 

Plate  X.Y.,Jig.  3,  represents  a spheric-headed  niche  in  a straight  wall,  with 
four  arch-stones  on  each  side  of  the  keystone,  and  therefore  also  with  four 
horizontal  courses ; and  as  the  joints  are  broken,  if  we  begin  the  first  course 
with  four  whole  stones,  as  exhibited  on  the  plan.  No.  2,  the  next  course  will 
consist  of  three  whole  stones  and  two  half  stones  in  one  in  each  angle.  As  the 
stones  are  here  in  this  example  projected  on  the  plan  as  well  as  on  the  elevation, 
the  elevation.  No.  1,  not  only  exhibits  the  number  of  courses,  but  the  number 
of  stones  also  in  each  course. 

Fig.  2 represents  a spheric-headed  niche  in  four  courses  besides  the  key- 
stone. No.  2,  the  ground-plan  of  No.  1. 

It  may  be  observed,  once  for  all,  that  the  greater  the  dimensions  of  a niche, 
the  greater  must  also  be  the  number  of  courses  in  the  height. 

The  principles  for  cutting  the  stones  of  these  niches  is  the  same  as  has  al- 
ready been  explained  for  Plate  XIV. 


SECTION  XII.  — Construction  of  the  Moulds,  and  Formation  of  the  Stones,  for  Domes 
UPON  Circular  Planes,  as  in  Plate  XVII.,  Figs.  1 and  2. 


ON  THE  CONSTRUCTION  OF  SPHERICAL  DOMES. 

Since  walls  and  vaults  are  generally  built  in  horizontal  courses,  the  sides  of 
the  coursing-joints  in  spherical  domes  are  the  surfaces  of  right  cones,  having  one 

18 


138 


PRACTICAL  MASONRY. 


common  vertex  in  the  centre  of  the  spheric  surface,  and  one  common  axis  ; 
hence  the  conic  surfaces  will  terminate  upon  the  spheric  surface  in  horizontal 
circles : again,  because  the  joints  between  any  two  stones  of  any  course  are  in 
vertical  planes  passing  through  the  centre  of  the  spheric  surface,  the  planes 
passing  through  all  the  joints  between  every  two  stones  of  every  course  will 
intersect  each  other  in  one  common  vertical  straight  line  passing  through  the 
centre  of  the  spheric  surface. 

The  line,  in  which  all  the  planes  which  pass  through  the  vertical  joints  inter- 
sect, is  called  the  axis  of  the  dome. 

Because  a straight  line  drawn  through  the  centre  of  a spheric  surface,  per- 
pendicular to  any  plane  cutting  the  spheric  surface,  will  intersect  the  cutting 
plane  in  the  centre  of  the  circle  of  which  the  circumference  is  the  common  sec- 
tion of  the  plane  and  spheric  surface,  the  axis  of  the  dome  will  intersect  all  the 
circles  parallel  to  the  horizon  in  their  centre. 

The  circumference  of  the  horizontal  circle,  which  passes  through  the  centre 
of  the  spheric  surface,  is  called  the  equatorial  circumference,  and  any  portion  of 
this  circumference  is  called  an  equatorial  arc. 

The  circumferences  of  circles,  which  are  parallel  to  the  equatorial  circle,  are 
called  parallels  of  altitude,  and  any  portions  of  these  circumferences  are  called 
arcs  of  the  parallels  of  altitude. 

The  intersection  of  the  axis  and  the  spheric  surface  is  called  the  pole  of  the 
dome. 

The  arcs  between  the  pole  and  the  base  of  the  dome,  of  the  circles  formed 
on  the  spheric  surface  by  the  planes  which  pass  along  the  axis,  are  called  merid- 
ians, and  any  portions  of  these  meridians  are  called  meridional  arcs. 

The  conical  surfaces  of  the  coursing-joints  terminate  upon  the  spheric  surface 
of  the  dome  in  the  parallels  of  altitude,  and  the  surfaces  of  the  vertical  joints 
terminate  in  the  meridional  arcs. 

Hence  in  domes,  where  the  extrados  and  intrados  are  concentric  spheric  sur- 
faces to  apparent  sides  of  each  stone  contained  by  two  meridional  arcs,  and  the 
arcs  of  two  parallel  circles  are  spheric  rectangles,  the  two  sides  which  form  the 
vertical  joints  are  equal  and  similar  frustrums  of  circular  sectors,  and  the  other 
two  sides,  forming  the  beds,  are  frustrums  of  sectors  of  conic  surfaces. 

In  the  execution  of  domes,  since  the  courses  are  placed  upon  conical  beds 
which  terminate  upon  the  curved  surfaces  in  the  circumferences  of  horizontal 
circles,  they  are  comprised  between  horizontal  planes,  and  therefore  may  be 
said  to  be  horizontal.  Hence  the  general  principle  of  forming  the  stones  of  a 
niche  constructed  in  horizontal  courses  may  likewise  be  applied  in  the  construc- 
tion of  domes. 


y\'.WMVx. 


CONSTRUCTION  OF  THE  MOULDS. 


139 


Each  of  the  stones  of  a course  is  first  formed  into  six  such  faces  as  will  be 
most  convenient  for  drawing  the  lines,  which  form  the  arrises  between  the  real 
faces.  Two  of  these  preparatory  faces  are  formed  into  uniform  concentric  cy- 
lindric  surfaces,  passing  through  the  most  extreme  points  of  the  axal  section 
of  the  course  in  which  the  stone  is  intended  to  be  placed,  the  axis  of  the  dome 
being  the  common  axis  of  the  two  cylindric  surfaces  of  every  course. 

Two  of  the  other  surfaces  are  so  formed  as  to  be  in  planes  perpendicular  to 
the  axis  of  the  dome,  and  to  pass  through  the  most  extreme  points  of  the  axal 
or  right  sections  of  the  course,  as  was  the  case  with  the  two  cylindric  surfaces. 

The  extreme  distance  of  the  two  remaining  surfaces  depends  upon  the  num- 
ber of  stones  in  the  course.  These  surfaces  are  in  planes  passing  through  the 
axis,  and  are  therefore  perpendicular  to  the  other  two  planes.  As  these  planes, 
which  pass  through  the  axis,  from  the  vertical  joints,  they  remain  permanent, 
and  undergo  no  alteration  except  in  the  boundary,  which  is  reduced  to  the 
figure  of  the  axal  section  of  the  course. 

In  order  to  find  the  terminating  lines  of  the  last  and  permanent  faces,  draw 
the  figure  of  the  section  of  the  course  upon  one  of  the  two  vertical  joints  in  its 
proper  position,  then  two  of  the  corners  of  the  mould  will  be  in  the  two  cylin- 
dric surfaces,  one  point  in  the  one,  and  the  other  in  the  other,  and  the  two  re- 
maining corners  of  the  mould  will  be  in  the  two  surfaces  which  are  perpendicular 
to  the  axis,  one  point  of  the  mould  being  in  the  one  plane  surface,  and  the  other 
point  in  the  other  plane  surface. 

Draw  a line  on  each  of  the  cylindric  surfaces  through  the  point  where  the 
axal  section  meets  the  surface  parallel  to  one  of  the  circular  edges,  and  the  line 
thus  drawn  on  each  of  the  cylindric  surfaces  will  be  the  arc  of  a cii’cle  in  a 
plane  perpendicular  to  the  axis  of  the  two  cylindric  surfaces,  and  will  be  equal 
and  similar  to  each  of  the  edges  of  the  cylindric  surface  to  which  it  is  parallel ; 
but  in  the  first  course  of  a hemispheric  dome,  there  will  be  no  intermediate  line 
on  the  convex  side,  since  the  circular  arc  terminating  the  lower  edge  will  also 
be  the  arris-line  of  the  convex  spheric  surface  and  the  lower  bed  of  the  stone, 
which  in  this  course  is  a plane  surface. 

In  all  the  intermediate  courses  of  the  dome  between  the  summit  and  the  first 
course,  the  line  drawn  on  the  convex  cylindric  surface  will  be  the  arris-line 
between  the  convex  spheric  surface  and  the  convex  conic  surface  which  forms 
the  lower  bed  of  the  stone ; and  in  all  the  courses  from  the  base  to  the  summit, 
the  line  drawn  on  the  concave  cylindric  surface  will  be  the  arris-line  between 
the  concave  conic  surface  forming  the  upper  bed  and  the  concave  spheric  sur- 
face of  the  stone,  which  concave  surface  will  form  a portion  of  the  interior  sur- 
face of  the  dome. 


140 


PRACTICAL  MASONRY. 


On  the  upper  plane  surface  of  each  stone  to  be  wrought  for  the  first  course, 
draw  a line  parallel  to  one  of  the  circular  edges ; but  in  each  of  the  stones  for 
the  intermediate  courses  between  the  first  course  and  the  keystone  at  the  sum- 
mit, draw  a line  on  each  of  the  planes  which  are  perpendicular  to  the  axis  par- 
allel to  either  of  the  edges  of  the  face  upon  which  the  line  is  made  through  the 
common  point  in  the  vertical  plane  of  the  joint  and  the  horizontal  plane,  then 
the  line  drawn  on  the  top  of  every  stone  will  be  the  arris-line  between  the  con- 
vex spheric  and  the  concave  conic  surfaces  to  be  formed,  and  the  line  drawn  on 
the  under  side  of  any  stone  in  each  of  the  intermediate  courses  will  be  the 
arris  between  the  convex  conic  and  the  concave  spheric  surfaces  to  be  formed  ; 
that  is,  between  the  surfaces  which  will  form  the  lower  bed  and  a portion  of  the 
interior  surface  of  the  dome. 

Draw  the  form  of  the  section  of  the  course  upon  the  plane  of  the  other  joint, 
so  that  the  corners  of  the  quadrilateral  figure  thus  drawn  may  agree  with  the 
four  lines  drawn  on  the  two  cylindric  and  on  the  two  parallel  plane  surfaces. 

Lastly,  reduce  the  stone  to  its  ultimate  figure  by  cutting  away  the  parts  be- 
tween every  two  adjacent  lines  which  are  to  form  the  arrises  between  every 
two  adjacent  surfaces,  until  each  surface  acquire  its  desired  form. 

Each  of  the  spherical  surfaces  must  be  tried  with  a circular  edged  rule,  in 
such  a manner  that  the  plane  of  curve  must  in  every  application  be  perpendic- 
ular to  each  of  the  arris-lines,  the  mould  for  the  convex  spheric  surface  being 
concave  on  the  trying  edge,  which  must  be  a portion  of  the  convex  side  of  the 
section,  1,  and  the  mould  for  the  concave  side  convex  on  the  trying  edge, 
and  a portion  of  the  concave  arc  forming  the  inside  of  the  section. 

The  two  conical  surfaces  of  the  beds,  and  the  two  plane  surfaces  of  the  ver- 
tical joints,  must  be  each  tried  with  a straight  edge,  in  such  a manner  that 
the  trying  edge  must  always  be  so  placed  as  to  be  in  a plane  perpendicular  to 
each  of  the  circular  terminating  arcs;  so  that  the  surfaces  between  these  arcs 
must  always  be  prominent  until  the  trying  edge  coincide  with  the  two  circular 
edges,  and  every  intermediate  point  of  the  trying  edge  with  the  surface. 

Fig.  3,  Let  Ab  c def . . . . ij  he  the  exterior  curve  of  the  section  divided  into 
the  equal  parts  A b,  be,  c d,  &lc.,  at  the  points  b,  c,  &.C.,  so  that  each  of  the 
chords  A b,  b c,  c d,  &,c.,  may  be  equal  to  the  breadth  of  the  stones  in  each  of  the 
circular  courses  ; also  \ei  ghij  kl  . . . . x be  the  inner  cune  of  the  section,  di- 
vided likewise  into  the  equal  arcs  gh,  hi,  i J,  See.,  by  the  radiating  lines  bh,  c i, 
Sec.-,  hence  Abhg  is  a right  section  of  the  first  course;  and,  therefore,  the 
figure  of  the  joint  at  each  end  of  every  stone  in  the  first  course  ; likewise  bcih  is 
the  right  section  of  the  second  course  ; and,  therefore,  the  figure  of  the  joint  at 
each  end  of  every  stone  in  the  second  course. 


CONSTRUCTION  OF  THE  MOULDS. 


141 


Since  the  entire  exterior  curve  of  the  axal  section  of  the  dome  is  divided 
into  equal  parts  alike  from  the  basis  on  each  side  of  the  section  ; and  since  the 
exterior  and  interior  sides  of  the  section  are  each  a semicircular  arc,  and  described 
from  the  same  centre ; and  since  the  dividing  lines  b h,  c i,  &lc.,  radiate  to  this 
centre,  all  the  sections  of  the  courses  and  the  boundaries  of  the  vertical  joints  will 
be  equal  and  similar  figures  ; and,  therefore,  a mould  made  to  the  figure  of  the 
section  of  any  course  will  serve  for  the  vertical  joints  of  all  the  stones. 

Fig.  4 exhibits  one  fourth  part  of  the  plan  of  the  convex  side  of  the  dome, 
showing  the  number  of  courses  and  the  number  of  stones  in  each  quarter-course, 
there  being  three  stones  of  equal  length  in  each  quarter-course. 

In  the  first  or  bottom  course,  7U  nop  is  the  plan  of  the  convex  side  of  one  of 
the  stones,  and  m'n'o'p  the  plan  of  the  concave  side  of  the  same  stone  ; and,  in 
the  second  course,  q vs  t is  the  plan  of  the  convex  side  of  one  of  the  stones,  and 
q'r's't'  is  the  plan  of  the  concave  side  of  the  same  stone ; so  that  in  the  first 
course  m n op'  is  the  figure  of  the  top  and  bottom  of  one  of  the  ring-stones,  p o 
is  the  intermediate  line  on  the  top,  and  m'n  that  on  the  bottom,  and  so  on  for 
the  remaining  stones. 

All  the  stones  of  any  course  being  equal  and  similar  solids,  and  alike  situated, 
the  same  mould  which  serves  to  execute  any  stone  of  any  one  course  will  serve 
to  execute  every  stone  of  that  course ; but  every  course  must  have  a difierent 
set  of  moulds  from  those  of  another,  except  the  figures  of  the  vertical  joints,  which 
will  be  all  found  by  one  mould,  as  has  been  already  observed. 

The  reader,  who  has  a competent  knowledge  of  the  construction  of  niches  in 
horizontal  courses,  will  not  be  at  anv  great  loss  to  understand  the  construction  of 
domes  ; or  if  the  construction  of  domes  is  well  understood,  lie  cannot  be  at  any 
loss  to  comprehend  the  construction  of  niches  ; however,  as  there  are  many  ob- 
servations respecting  the  construction  of  domes  that  do  not  apply  to  niches,  par- 
ticularly as  the  dome  in  the  present  article  has  two  apparent  sides,  in  order  to 
prevent  the  reader  from  wasting  his  time  in  referring  to  both  articles,  we  shall 
here  conduct  him  thi-ough  the  formation  of  one  of  the  stones  in  the  first  two 
courses,  the  figure  of  the  stones  in  the  remaining  courses  being  found  in  a similar 
manner. 

In  fig.  3,  draw  A D perpendicular  to  the  ground-line  A y,  and  through  h draw 
B C also  perpendicular  to  the  ground-line  A y.  Now  A B as  well  as  Ag-  being 
upon  the  ground-line,  therefore  to  complete  the  rectangle  A B C D,  so  as  to  cir- 
cumscribe the  section  A h h g,  and  to  have  two  vertical  and  two  horizontal  sides, 
draw  through  the  point  b the  remaining  side  D C parallel  to  A y. 

The  rectangle  A B C D is  the  section  of  a circular  course  of  stone,  or  that  of  a 
ring  contained  by  two  vertical  concentric  uniform  cylindric  surfaces  and  by  two 


142 


PRACTICAL  MASONRY. 


horizontal  plane  rings,  the  radius  of  the  concave  cylindric  surface  being  a B,  and 
the  radius  of  the  convex  cylindric  surface  being  a A,  and  the  height  of  the  ring 
being  A D or  B C. 

Make  a mould  to  the  plan  of  one  of  the  stones  in  the  first  course,  that  is,  to 
m no p,  Jig.  4, 

From  any  point  y,Jig.  5,  with  a radius  z rn,  jig.  4,  or  the  radius  a A,  Jig.  3,  de- 
scribe the  arc  m n.  Make  the  arc  m n,  Jig.  5,  equal  to  the  arc  m n,  Jig.  4,  and 
draw  the  lines  m u and  n v radiating  to  the  point  y.  Again,  from  the  centre  y,  and 
with  the  radius  a B,  Jig.  3,  describe  the  arc  v u. 

Make  a face-mould  to  m nv  u,  and  this  mould  will  serve  for  drawing  the 
figure  of  the  two  horizontal  surfaces  of  each  stone  in  the  first  or  bottom. 

To  cut  one  of  the  stones  in  the  first  course  to  the  required  form : — Reduce 
the  stone  from  one  of  the  sides  till  the  surface  becomes  a plane.  Apply  the 
mould  made  to  the  figure  mnv  u on  this  surface,  which  is  one  of  the  two  hori- 
zontal faces,  and  having  drawn  the  figure  of  the  mould,  reduce  the  stone  so  as  to 
form  three  of  the  arris-lines  of  the  faces,  which  are  to  be  vertical,  and  these  arris- 
es 'vill  be  square  to  the  face  already  wrought.  On  each  of  the  three  arrises  thus 
formed,  set  the  height  of  the  stone  from  the  plane  surface  already  made ; reduce 
the  substance  till  the  surface  becomes  a plane  parallel  to  that  first  formed. 

Apply  then  the  face-mould  in  n v u upon  the  plane  surface  last  wrought,  so 
that  three  points  of  the  mould  may  join  the  corresponding  points  in  the  meeting 
of  the  three  arrises,  and,  having  drawn  the  figure  of  the  mould  upon  the  second 
formed  face,  run  a draught  on  the  outside  of  each  line  upon  each  of  the  inter- 
mediate surfaces  from  each  of  the  parallel  faces.  So  that  there  will  be  four 
draughts  receding  from  the  face  first  formed,  and  four  receding  from  the  face  last 
formed,  and  that  upon  the  whole,  including  the  two  draughts  upon  each  side  of 
each  of  the  four  perpendicular  arrises,  there  will  be  sixteen  in  all. 

The  two  draughts  along  the  edges  of  the  convex  cylindric  surface  to  be  formed 
must  be  tried  with  a concave  circular  rule,  made  to  the  form  of  the  arc  mn,Jig.  4, 
and  the  two  draughts  along  the  edges  of  the  concave  cylindric  surface  must  be 
tried  with  a convex  circular  rule  made  to  the  form  of  the  arc  po,  Jig.  4.  More- 
over, the  two  draughts  which  are  made  along  each  of  the  edges  of  each  opposite 
intermediate  plane  surface  must  be  tried  with  a straight  edge. 

Having  regularly  formed  the  draughts,  so  that  the  circular  and  straight  edges  of 
each  of  the  three  rules  may  coincide  in  all  points  with  the  bottom  surface  of  each 
respective  draught,  and  with  the  arris-line  at  each  extremity,  the  workman  may 
then  cut  away  the  superfluous  parts  of  the  stone,  as  far  as  he  can  discern  to  be 
just  prominent,  or  something  raised  above  the  four  draughts,  bordering  the  four 
edges  of  each  of  these  surfaces. 


CONSTRUCTION  OF  THE  MOULDS. 


143 


The  rough  part  of  the  operation  being  done,  each  of  the  four  intermediate 
faces  may  be  brought  to  a smooth  surface  and  to  the  required  form,  by  means  of 
a common  square  ; the  face  of  coincidence  of  the  stock,  or  thick  leg,  being  ap- 
plied upon  one  of  the  two  parallel  faces,  and  the  thin  leg,  called  the  blade,  to  the 
surface  of  the  stone,  in  the  act  of  reducing,  until  it  has  acquired  the  figure  desired, 
or  the  two  cylindric  surfaces  may  also  be  tried  by  means  of  circular  edged  rules, 
the  edge  of  each  rule  being  placed  so  as  to  be  parallel  to  one  of  the  parallel 
faces  ; a concave  circular  edge  being  applied  upon  the  convex  side,  and  a con- 
vex circular  edge  upon  the  concave  side. 

The  six  faces  which  contain  the  solid  being  thus  formed,  we  shall  now  proceed 
to  find  the 'upper  arris : — for  this  purpose  apply  the  mould  made  to  the  form 
mn  0 p,  Jig.  4,  upon  the  top  of  the  stone  drawn  by  the  means  of  the  mould 
mnvu, Jig.  5. 

Suppose  m iiv  u,Jig.  5,  to  be  the  figure  drawn  on  the  top  of  the  stone  itself,  by 
means  of  the  mould  made  to  ?n  n v u ; and  mno  p^fig.  5,  to  be  the  mould  made 
from  mn  op,  Jig.  4.  Lay  the  edge  mii,Jig.  4,  upon  the  edge  mn,Jig.  5,  on  the 
top  of  the  stone,  so  that  the  equal  circular  arcs  may  coincide  in  all  their  points ; 
and  draw  the  line  op  along  the  concave  edge  of  the  mould,  and  op  will  be  the 
arris-line  of  the  spherical  and  conical  surfaces  which  are  yet  to  be  formed. 

Let  the  rectangle  m n nm\  Jig.  6,  be  the  elevation  of  the  convex  cylindric 
surface  of  the  same  stone,  projected  on  a plane  parallel  to  each  of  the  chords  of 
the  circular  arcs  and  to  one  of  the  straight  arrises  of  this  surface ; the  straight 
line  m n representing  the  upper  circular  edge,  m m,  n n,  the  two  vertical  arrises ; 
so  that  the  convex  spherical  surface  is  terminated  at  the  top  by  the  arc  o p and  at 
the  bottom  by  the  arc  iim'. 

Let  the  rectangle  nmm'n,  Jig.  7,  be  the  elevation  of  the  concave  cylindric  face, 
projected  on  a plane  parallel  to  one  of  the  chords  of  one  of  the  circular  bounda- 
ries and  to  one  of  the  straight-lined  boundaries  of  this  face ; then  the  upper  and 
lower  planes  will  be  projected  into  the  parallel  lines  n m,  n'm'.  Therefore  all  the 
lines  of  each  of  these  three  planes  will  be  projected  upon  the  lines  n m,  n'm\  and 
as  the  rectilineal  figure  formed  by  the  two  chords  and  the  two  straight  lines  is 
parallel  to  the  plane  of  projection,  it  will  be  projected  into  an  equal  and  similar 
figure ; therefore  the  projected  figure  is  a rectangle,  and  the  sides  n m,  n'm\  are 
equal  to  each  other,  and  to  the  chords  of  the  two  circular  arcs ; and  the  lines  m'm, 
n n',  are  each  equal  to  the  height  of  the  hollow  cylinder,  or  equal  to  the  distance 
between  the  parallel  planes. 

Hence  the  concave  surface  will  be  projected  also  into  a rectangle,  and  the 
middle  of  the  chords  of  the  arcs  terminating  the  parallel  edges  of  the  concave 
surface  upon  the  middle  of  the  chords  of  the  arcs  terminating  two  of  the  oppo- 


144 


PRACTICAL  MASONRY. 


site  edges  of  the  convex  surface,  as  also  the  two  opposite  parallel  straight-lined 
sides  in  the  height  of  the  solid  will  be  projected  into  straight  lines  equidistant 
from  the  projections  of  the  corresponding  lines  in  the  height  of  the  solid  on  the 
convex  side. 

Therefore,  the  straight  lines  nn\  mm,  vv\  uu,  are  all  equal  to  the  height  of 
the  hollow  cylindric  solid,  or  equal  to  the  distance  between  the  parallel  planes  and 
the  distance  between  the  lines  n n,  v v',  equal  to  the  distance  between  the  lines 
m m\  u u'. 

To  form  the  common  termination  between  the  upper  conical  and  the  lower 
spherical  surfaces,  let  v v,  u u,  represent  the  concave  cylindric  surface ; and 
therefore  v o',  u u',  will  represent  the  opposite  circular  arcs,  which  tenninate  two 
of  the  sides  of  this  concavity.  Upon  this  surface  draw  the  line  v"  u",  parallel 
to  the  circular  edge  v it,  on  the  top  at  the  distance  hC,fig.  3,  and  the  line  vi"u" 
will  be  the  arris  now  required  between  the  concave  conic  surface  at  the  top  and 
the  concave  spheric  surface,  these  two  surfaces  being  as  yet  to  be  formed. 

To  form  the  remaining  and  common  termination  of  the  concave  spherical  sur- 
face, and  the  lower  or  level  bed  of  the  stone : — Draw  a circular  arc  on  the  level 
surface,  underneath  parallel  to  the  circular,  to  the  circular  edge  on  the  lower  edge 
of  the  concave  cylindric  surface,  and  this  line  will  be  the  remaining  arris  required. 

The  two  cylindric  surfaces,  and  the  upper  plane  surface,  are  entirely  cut  away ; 
but  the  intermediate  line  drawn  on  the  top,  and  that  drawn  on  each  cylindric  sur- 
face, remain,  as  well  as  the  outer  edge  of  the  lower  bed. 

To  form  the  intermediate  faces  of  the  stone  into  the  two  upper  and  lower 
conical  beds,  and  into  the  two  apparent  concave  and  convex  spherical  surfaces: 
Reduce  each  side  of  the  solid  as  near  to  the  required  surface  as  possible,  so  that 
all  the  intermediate  parts  between  the  arrises  or  lines  drawn  on  the  former  faces 
may  be  prominent. 

Suppose,  then,  that  we  proceed  to  finish  the  stone  required  to  be  formed  in 
the  following  order : first,  by  proceeding  with  the  convex  spherical  surface ; 
secondly,  the  upper  concave  conical  surface ; thirdly  and  lastly,  the  concave 
spherical  surface.  Having  approached  as  nearly  to  the  required  surfaces  as  can 
be  done  with  safety,  the  upper  conical  concave  surface  will  be  reduced  to  its  ulti- 
mate form  by  cutting  away  the  substance  carefully,  so  that  the  surface  between 
the  two  arris-lines  may  at  last  coincide  with  all  the  points  of  a straight  edge  ap- 
plied perpendicularly  to  the  two  arrises. 

The  convex  spherical  face  will  be  formed  ultimately  by  cutting  the  sub- 
stance of  the  stone  carefully,  so  that  the  surface  between  the  arris-line  on  the 
top  and  the  circular  convex  arris-line  on  the  outside  of  the  lower  bed  may  at 
last  agree  with  all  the  points  of  the  circular  concave  edge  of  the  rule  made  to  a 


CONSTRUCTION  OF  THE  MOULDS. 


145 


portion  of  the  arc  A 6 c d,  fig.  3,  of  the  section  of  the  dome.  This  circular  edged 
rule  must  be  frequently  applied ; and  in  each  application  the  plane  of  the  arc 
must  be  perpendicular  to  the  surface,  gradually  approaching  to  its  required 
sphericity. 

To  form  the  concave  surface  of  the  upper  bed  of  the  stone,  reduce  the  solid, 
by  carefully  cutting  parts  away,  so  as  at  length  the  surface  between  the  upper 
arris  and  the  intermediate  line  drawn  on  the  inside  formerly  concave  may  coin- 
cide with  all  the  points  of  a straight  edge  applied  perpendicularly  to  the  upper 
arris-line  from  any  point  of  this  arris. 

The  concave  spherical  surface  will  be  formed  in  the  same  manner  as  the  con- 
vex spherical  surface  already  supposed  to  be  formed,  with  this  difference,  that 
the  circular  edge  which  proves  the  sphericity,  by  trial,  must  be  convex  instead  of 
being  concave.  This  convex  surface  lies  between  the  lower  arris,  terminating 
the  upper  conic  bed,  and  the  inner  arris  of  the  lower  bed. 

As  to  the  lower  bed,  it  is  already  formed,  being  part  of  the  plane  surface,  for- 
merly one  of  the  ends  of  the  hollow  cylinder,  in  a plane  perpendicular  to  the  com- 
mon axis;  and  as  to  the  ends  forming  the  vertical  joints,  they  were  at  first  form- 
ed in  making  the  hollow  cylindric  solid;  so  that  one  of  the  stones  in  the  lower 
course  is  now  finished. 

One  of  the  stones  in  the  second  course  being  first  formed  into  the  frustrum  of 
a cylindric  wedge,  as  was  done  with  the  stone  formed  for  the  first  course,  the 
several  faces  which  contain  this  solid  are  as  follow:  — grxw,  fig.  5,  represents 
the  plane  truncated  sector  forming  the  top,  s t being  the  arris-line  between  the 
spheric  surface  on  the  convex  side  of  s t,  and  the  conic  surface  in  the  concave 
side  of  st ; gr  r'g',  fig.  8,  the  convex  cylindric  surface,  g"r  r"  the  arris  between 
the  convex  spheric  and  the  convex  conic  surfaces,  and  rggr,  fig.  9,  the  con- 
cave cylindric  surface;  x"w'\  the  arris  between  the  concave  spheric  surface  un- 
derneath and  the  concave  conic  surface  above,  the  arris-line  being  drawn  upon 
the  lower  plane  surface ; we  shall  thus  have  the'  arris-lines  between  the  spheric 
and  conic  surfaces. 

The  solid  being  cut  as  before  directed  between  the  arris-lines  until  the  surfaces 
are  duly  formed,  we  shall  have  also  one  of  the  stones  in  the  second  course  com- 
pletely prepared  for  setting. 

Perhaps  for  preparing  the  stones  for  the  first  and  second  courses,  as  also  the 
stones  near  the  summit,  no  better  method  can  be  followed  than  that  which  we 
have  employed  in  preparing  a stone  in  each  of  the  two  lower  courses ; yet,  as  the 
saving  of  an  expensive  material  and  labor  is  a desirable  object,  we  shall  here  show 
how  the  waste  of  stone  and  the  labor  of  the  workman  may  in  a considerable 
degree  be  prevented. 


19 


146 


PRACTICAL  MASONRY. 


plate  XVIII. -another  method. 

Let  fig.  1 be  the  section  of  the  dome,  and  fig.  2 a plan  of  the  same,  showing 
the  convex  side.  Now,  as  the  saving  of  material  will  be  principally  in  the  stones 
which  constitute  the  intermediate  courses,  we  shall  select,  for  an  example,  the 
fifth  stone  from  the  bottom  and  from  the  summit.  The  section  of  this  stone  is 
abed,  fig.  1 . 

Draw  de  parallel,  and  ae  perpendicular,  to  the  base  of  the  dome.  Then,  in- 
stead of  first  working  the  sides  of  the  stone,  so  that  the  section  may  be  a rectan- 
gle, of  which  two  sides  are  parallel  and  two  perpendicular  to  the  horizon,  let  it 
be  wrought  into  the  form  abode,  so  that  the  part  d e may  be  parallel  to  the 
horizon. 

Let  the  section  ab  c de  he  transferred  to  No.  1,  at  abc  de,  and  let  f g hi,  No.  I, 
be  the  section  of  the  rough  stone,  out  of  which  the  coursing-stone  of  the  dome  is 
to  be  wrought ; the  sides  of  the  section  of  the  rough  stone  having  two  parallel 
and  two  perpendicular  faces  to  the  lower  bed  of  the  stone.  The  wrought  stone 
must  be  selected  sufficiently  large,  so  that,  when  it  is  reduced  to  the  intended 
form,  all  the  spherical  and  conical  surfaces  must  be  entire,  and  thus  the  arrises 
will  also  be  entire. 

The  first  operation  is  to  reduce  the  stone  by  taking  away  a triangular  prism 
from  the  top  ; the  section  of  which  prism  is  represented  by  kli.  No.  I,  so  that 
the  surface,  of  which  the  section  is  d e,  may  be  a plane  surface. 

No.  2 is  an  orthographical  projection  of  the  stone,  of  which  the  section  is 
mnop,  after  being  thus  reduced,  grst  representing  the  plane  surface,  of  which 
the  section  kl.  No.  1,  is  parallel  to  the  plane  of  projection.  On  the  plane 
surface  grst.  No.  2,  apply  a mould  xiivw,  so  that  the  radius  of  the  curved 
edge  uv  may  be  equal  to  the  line  dx,jig.  1,  dx  being  parallel  to  the  base, 
meeting  the  axis  in  x,  and  that  v u and  wx  may  be  straight  lines  tending  to  the 
centre  of  the  arc  ux;  and  that  the  chord  of  the  arc  ux  may  be  equal  to  the 
length  of  the  chord  of  the  upper  arris  of  the  stone.  Draw  lines  along  x u,  u v,  and 
IV  V,  of  the  mould,  and  let  v iv  be  the  line  drawn  by  the  curved  edge  v re  of  the 
mould,  u V the  line  drawn  by  the  straight  edge  u v of  the  mould,  and  x rv  the  line 
drawn  by  the  straight  edge  x w of  the  mould. 

Take  the  mould  away,  and  there  will  remain  the  three  lines,  namely,  the  arc 
V IV,  and  the  straight  lines  v u and  iv  x,  which  radiate  to  the  centre.  Then  v to  is 
the  upper  arris  of  the  stone, and  the  straight  lines  v u and  wx  are  in  the  planes  of 
the  meeting  joints  of  the  two  adjacent  stones,  in  the  same  course,  to  that  which  is 
now  in  the  act  of  working. 

The  second  operation  is  to  work  the  spherical  surface  by  means  of  the  bevel 


CONSTRUCTION  OF  THE  MOULDS. 


147 


edc,Jig.  1,  in  such  a manner,  that  while  the  point  d is  upon  any  point  of  the 
arc  V tc,  No.  2,  the  straight  edge  d e may  coincide  with  the  plane  surface  x u v w. 
No.  2,  and  the  curved  edge  d c may  coincide  with  the  spherical  surface  required 
to  be  formed,  and  lastly,  that  the  plane  of  the  bevel  cde  may  be  perpendicular 
to  the  arris -line  v w. 

The  third  operation  is  to  find  the  vertical  joints  of  the  stone : these  will  be 
formed  by  means  of  a common  square,  of  which  the  right  angle  is  contained  by 
two  straight  lines,  so  that  when  the  vertex  of  the  angle  of  the  square  is  upon 
any  point  of  the  line  v lo  or  u x,  No.  2,  the  inner  face  of  application  of  the  third 
part  must  be  upon  the  plane  surface  t u v iv,  and  the  edge  of  application  of  the 
thin  part  upon  the  vertical  joint,  and  that  both  edges  of  application  may  be  per- 
pendicular to  the  line  v tc  or  u x. 

The  fourth  operation  is  to  form  the  conical  upper  bed  of  the  stone  by  means 
of  the  bevel  fgh,fig.  1,  so  that  when  this  conic  surface  is  wrought  to  the  re- 
quired form,  and  the  vertex  g of  the  angle  is  applied  upon  any  point  of  the  curve 
uv,^o.  2,  the  curved  edge  ^ A may  then  coincide  with  the  spherical  surface, 
and  the  straight  edgeg-/  with  the  conical  bed  thus  formed,  the  edges  and 
gh  being  perpendicular  to  the  arris  ux. 

Thus  four  sides  of  the  stone  are  now  formed,  namely,  the  convex  spherical 
surface,  the  concave  conical  surface,  and  the  two  vertical  joints  of  the  stone. 
By  gauging  the  spherical  surface  to  its  breadth,  the  under  or  convex  conical  sur- 
face may  be  formed  by  means  of  the  same  bevel  f g h,  fig.  1,  and  gauging  the 
sides  of  the  stone  which  form  the  joints,  namely,  the  concave  and  convex  conic 
surfaces  which  form  the  upper  and  lower  beds,  and  the  two  vertical  joints  from 
the  spherical  convex  surface,  we  shall  now  be  enabled  to  form  the  concave 
spherical  surface  by  means  of  a slip  of  wood,  of  which  one  edge  is  formed  to 
the  curve  of  the  inside  of  the  section.  No.  1,  and  thus  we  have  formed  a stone 
of  the  fifth  course,  as  required  to  be  done.  In  the  same  manner  the  stones  of 
every  course  may  be  formed. 

This  method  will  never  require  so  much  stone  as  the  former  or  first  method 
nor  yet  the  quantity  of  workmanship ; but  it  requires  greater  care  in  the  execu- 
tion. This  last  method  was  used  in  the  construction  of  the  dome  of  the  Hun- 
terian Museum  at  Glasgow. 

To  execute  a vault,  of  which  both  the  extrados  and  intrados  are  conic  sur- 
faces, having  a common  vertical  axis,  the  solid  being  equally  thick  between  the 
conic  surfaces,  so  that  in  the  joint  lines  those  of  beds  may  be  horizontal,  and 
those  of  the  headings  in  vertical  planes  passing  along  the  axis. 

The  easiest  method  of  executing  this  is,  to  form  the  beds  so  that  when  built 
they  will  unite  in  horizontal  planes,  and  the  headings  in  vertical  planes. 


148 


PRACTICAL  MASONRY. 


Let  ABC,  fig.  3,  be  a section  of  the  exterior  surface,  and  E F G a section  of 
the  interior  surface  ; the  lines  A B and  E F being  parallel,  as  also  the  lines  C B 
and  GF. 

In  order  for  the  easy  application  of  the  bevels,  it  will  be  convenient  to  wwk 
the  exterior  faces  of  the  stones  first  as  plane  surfaces  ; then  form  the  joints  by 
means  of  a face-mould,  and  the  angles  which  the  joints  make  with  the  planes  of 
the  faces  by  means  of  the  bevels,  and  lastly,  run  a draught  upon  each  end  of 
the  face  first  wrought,  according  to  the  proper  curve  of  the  cone. 

Let  dSv  he  the  exterior  line  of  the  plan,  D being  the  centre  of  all  the  circles 
which  form  the  seats  of  the  joint  lines  in  the  plan.  Divide  the  semicircular  arc 
(ISv  into  as  many  equal  parts  as  the  number  of  vertical  joints  in  the  semi- 
circumference. 

Let  there  be  five  stones,  for  instance,  in  each  quadrant ; therefore,  if  d S and 
S u be  quadrants,  divide  dS  into  five  equal  parts,  and  let  de  be  the  first  part. 
Through  the  point  e,  draw  the  radius /D.  Bisect  the  arc  de'mf,  and  draw  C / 
a tangent  to  the  semicircular  arc  dSv  at  the  point /.  Bisect  each  of  the  arcs 
between  the  points  of  division  in  the  quadrantal  arc  d S,  and  the  tangents  being 
drawn  at  each  point  of  bisection,  will  form  the  polygonal  base  Cf  mn  op. 

To  form  the  angle  of  the  mitre  at  the  meeting  of  two  heading-joints.  In  C /, 
or  C f produced,  take  any  point  g,  and  draw  gh  perpendicular  to  the  diameter 
A C,  meeting  A C in  the  point  h.  Draw  h i perpendicular  to  C B,  meeting  C B 
in  the  point  i.  In  D C make  hk  equal  to  hi  and  join  kg ; then  will  the  angle 
D^-  o-  be  the  bevel’ of  the  mitre. 

The  sections  of  each  of  the  stones  as  they  rise  being  de'b'G',  e'i'f'b',  i'fkf', 
the  dimensions  of  the  stones  will  be  found  as  follows.  Through  the  points 
e',  i',  f,  draw  the  straight  lines  dV, A’7',  intersecting  the  inner  line  GF  in 
the  points  b',/\  k'.  Through  6',/', //,  draw  the  lines  a b\  d'f',  h'k',  perpen- 
dicular to  A C.  Also  through  the  points  e\  i,j\  draw  eg,  i'l',  as  also  C c,  which 
will  complete  the  sections  of  the  stones.  The  other  side,  A E F B,  of  the  sec- 
tion exhibits  the  sections  of  the  stones  perpendicular  to  the  intrados  and  ex- 
trados  of  the  lines  ; the  sections  of  the  stones  being  A E r,  E /3  / r,  /3  y V t,  and 
the  sections  of  the  joints  E r,  (i  t,  y\.  To  find  the  curve  of  the  stone  at  any 
section,  as  E ?•  at  the  point  r.  With  the  horizontal  radius  5 r,  fig.  3,  and  from 
the  centre  5,  describe  an  arc  ;*3.  From  tbe  point  3,  draw  3 2 perpendicular  to 
5 r,  meeting  5 r in  2.  In  2 r make  2 1 equal  to  the  nearest  distance  between  the 
point  2 and  the  line  A B.  From  some  point  found  in  the  line  5 r,  describe  an 
arc  1 3,  and  the  arc  1 3 will  be  the  curvature  of  the  top  of  the  stone  at  the  joint. 
This  is  shown  at^^^.  4. 

Figs.  5 and  6 exhibit  another  method  of  finding  the  curve  at  the  joint,  by 
means  of  the  radius  of  curvature. 


19. 


Liniri 


H ll Sc. 


ON  RAKING  MOULDINGS. 


149 


SECTION  XIII.  — The  Manner  of  finding  the  Sections  of  Raking  Mouldings. 

To  find  the  raking  mouldings  of  a canted  bow-window,  with  munnions  and 
transoms. 

Let  the  plan  of  the  window  be  fig.  1,  Plate  XIX.,  consisting  of  three  sides, 
the  middle  one  being  parallel  to  the  walls,  and  the  other  two  at  an  angle  of  135 
degrees  each,  with  the  middle  face  of  the  window. 

Also,  let  r a Q,  fig.  2,  be  a horizontal  section  of  one  of  the  angles.  No.  1 being 
a right  section  of  one  of  the  munnions,  the  same  as  the  right  section  of  the  tran- 
som-sill or  lintel,  and  let  ar.  No.  2,  be  the  line  of  mitre  corresponding  to  AR, 
No.  1,  A R being  perpendicular  to  a Q. 

In  order  to  find  the  right  section.  No.  2,  of  the  angular  munnion.  In  the  curves 
of  the  given  section.  No.  1,  draw  lines  through  a sufficient  number  of  points 
perpendicular  to  a Q,  and  draw  a c perpendicular  to  a r ; transfer  the  points  B C 
from  A,  No.  1,  made  by  the  perpendiculars  to  No.  2;  from  a to  c upon  ac,  and 
from  a to  b through  the  points  in  a c,  draw  lines  parallel  to  a r,  to  intersect  the 
corresponding  lines  parallel  to  Q a from  the  assumed  points  K,  L,  M,  N,  in  the 
curves.  No.  1,  and  through  these  points  trace  the  curves  which  will  form  one 
side  of  the  section  No.  2 ; repeat  the  same  operation  on  the  other  side,  and  we 
shall  have  the  complete  section  required. 

Figs.  3 and  4,  No.  1,  is  the  right  section  of  the  raking  moulding  on  a pedi- 
ment, which,  if  supposed  to  be  given,  the  section  No.  2 may  be  found,  as  that  at 
No.  2,  from  No.  ^,fig.  2 ; but  in  this  case  No.  2 is  generally  that  which  is  given, 
and  the  section  No.  1 is  traced  therefrom. 

In  all  these  cases  of  raking  mouldings,  draw  a c perpendicular  to  a r,  the  line 
of  mitre.  To  find  any  point  m,  take  the  point  M in  the  section  No.  1,  and 
draw  M B perpendicular  to  A C,  Nos.  1 and  2,  meeting  A C in  B,  and  draw 
Mm  parallel  to  Rr.  Make  ab  equal  to  A B,  and  draw  bm  parallel  to  aj,  and 
m will  be  a point  in  the  curve.  In  the  same  manner  will  be  found  the  points 
;,  k,  /,  n,  No.  2,  from  the  points  J,  K,  L,  N,  No.  1 ; and  hence  the  section  No.  2 
may  be  traced  from  No.  1. 

Fig.  4 is  described  in  the  same  manner  as  fig.  3. 


150 


PRACTICAL  MASONRY. 


SECTION  XIV.  — Construction  of  a Lintel,  or  an  Architrave,  in  three  or  more  Parts, 
OVER  AN  Opening,  and  the  Steps  of  a Stair  over  an  Area. 

On  the  method  of  building  a lintel,  or  architrave,  with  several  stones,  so  that 
the  soffit  and  top  of  the  lintel,  or  architrave,  may  be  level ; and  that  the  con- 
necting joints  of  the  course  may  appear  to  be  vertical  in  the  front  and  rear  of 
the  lintel,  or  architrave. 

A lintel,  or  architrave,  is  frequently  formed  in  several  stones,  from  the  diffi- 
culty of  procuring  one  of  sufficient  length.  The  method  of  doing  this  is  founded 
upon  the  principle  of  arching,  the  arch  being  concealed  within  the  thickness  of 
the  stones. 

Fig.  5,  Plate  XIX.,  represents  the  upper  part  of  an  aperture,  lintelled  as  spe- 
cified in  the  contents  of  this  section  ; the  centre  of  the  radiating  joints  being 
the  vertex  of  an  equilateral  triangle. 

Fig.  6 represents  the  top  of  the  lintel,  exhibiting  the  thickness  of  the  radiat- 
ing joints,  and  the  thickness  of  the  square  joints  on  each  side  of  the  concealed 
arch. 

Fig.  7 represents  the  soffit  of  the  lintel,  exhibiting  the  joint  lines  perpendic- 
ular to  the  two  edges,  as  the  radiating  as  well  as  the  vertical  joints  all  terminate 
in  these  lines. 

No.  1 exhibits  the  first  abutment-stone  over  the  pier;  No.  2,  the  first  stone 
of  the  lintel ; No.  3,  the  second  stone,  which  forms  the  key  ; the  two  remaining 
stones  are  the  same  as  the  first  stone  of  the  lintel  and  the  abutment-stone,  being 
placed  in  reverse  order. 

The  three  stones  here  exhibited  show  the  manner  of  indenting  the  stones  so 
as  to  form  a series  of  wedges ; and  in  order  to  regulate  the  soffit,  the  radiations 
are  stopped  at  half  their  height. 

Fig.  1,  Plate  XXV.,  exhibits  the  method  of  constructing  an  architrave  over 
columns  when  the  stone  is  not  of  sufficient  length  to  reach  the  two  columns. 
No.  1,  plan  of  the  upper  horizontal  side  of  the  architrave,  exhibiting  a chain-bar 
of  wrought-iron,  with  collars  let  in  flush  with  the  top  bed,  the  sockets  being 
filled  with  melted  lead  round  the  collars. 

In  the  plan  and  elevation,  the  same  letters  express  different  sides  of  the  same 
parts  ; thus,  in  the  elevation,  1,  the  letter  A is  written  upon  the  part  express- 
ing the  vertical  face  of  the  stone,  over  the  angular  column  ; and  A,  on  the  plan 
No.  1,  expresses  the  horizontal  side  or  bed  of  the  same  stone.  The  letter  B, 
on  the  elevation  Jig.  1,  represents  the  vertical  face  of  the  middle  stone  of  the 


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n:iv.Wi/.ffw  Sr. 


IBIRKCK  BOOS' IDS 


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Briik  Arches. 


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fy  17. 


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w.n.wusoft  Si\ 


CONSTRUCTION  OF  A LINTEL. 


151 


architrave;  and  B,  on  the  plan,  represents  the  bed  of  the  middle  stone.  The 
letter  C,  on  the  elevation,  represents  the  vertical  face  of  the  stone  over  the  sec- 
ond column ; and  C represents  the  upper  horizontal  surface  or  bed.  The  stones 
A and  C serve  as  abutments  to  the  middle  stone  B,  which  is  let  in  in  the  man- 
ner of  a keystone,  and  therefore  acts  as  a wedge.  In  order  to  lessen  the  effect 
of  the  pressure  of  the  inclined  sides  from  forcing  the  columns  to  a greater  dis- 
tance, the  joint  onnmm  has  two  horizontal  wedges,  n w,  mm,  which  will  pre- 
vent the  middle  part  from  descending. 

D exhibits  a stone  in  the  act  of  setting,  and  is  let  down  by  means  of  a lewis ; 
a brick  arch  is  exhibited  over  the  architrave,  in  order  to  discharge  the  weight 
from  above,  and  is  resisted  by  the  abutments  at  the  ends.  The  lateral  pressure 
of  the  brick  arch,  and  of  the  stone  B,  is  entirely  counteracted  by  means  of  the 
chain-bar,  of  which  the  top  is  represented  in  No.  1. 

No.  3 exhibits  a section  of  the  work,  z being  a section  of  the  arch  in  the 
middle,  and  y shows  the  void  between.  The  right  section  through  the  middle 
of  the  arch  between  the  columns  is  the  same  as  shown  at  zyw. 

No.  2 exhibits  the  manner  of  cutting  the  joints  of  the  stones  over  the  column, 
g and  w being  the  steps  of  the  socket,  and  u u u the  square  part  of  the  joint. 

On  the  construction  of  stairs  over  an  area  to  an  entrance  door. 

Stairs  of  this  description,  which  consist  of  one  flight,  must  either  be  supported 
upon  a solid  foundation  raised  from  the  ground ; or,  if  over  a hollow,  the  steps 
must  be  supported  upon  a brick  arch,  or  otherwise,  by  working  the  soffits  in  the 
form  of  a concave  curve. 

F F represents  the  abutments  of  the  columns ; E,  the  steps ; G,  the  cantae, 
as  projecting  from  the  wall,  to  support  the  architrave-stone  D. 

Since  the  joints  should  always  be  perpendicular  to  the  curve,  they  must  all 
tend  to  the  centre  of  the  circle  which  forms  the  soffit ; and  since  the  steps 
should  rest  firmly  upon  one  another,  they  ought  to  rest  upon  a horizontal  sur- 
face. To  accomplish  these  ends,  every  joint  ^between  two  steps  ought  to  con- 
sist of  two  surfaces,  one  horizontal,  and  the  other  part  a plane,  radiating  to  the 
axis  of  the  cylinder,  of  which  the  soffit  of  the  steps  is  the  curved  surface. 

Fig.  5,  Plate  XV.,  is  the  plan,  fig.  I,  the  elevation,  of  a semicircular  arched 
door-w’ay,  built  of  wrought  stone,  with  steps,  and  fig.  2,  a section  of  the  same ; 
ab  is  the  curve-line,  representing  a section  of  the  soffits.  The  joints  are  here 
drawn  to  the  centre  c of  the  arc  a b. 

In  this  case,  where  there  are  no  brick  arches  below,  the  joints  should  be  plug- 
ged. Fig.  4 exhibits  a section  of  the  steps,  showing  the  plugs,  one  in  each  end 
perpendicular  to  the  surface  of  the  joint. 


152 


PRACTICAL  MASONRY. 


SECTION  XV. — Construction  of  the  Stones  for  Gothic  Vaults,  in  Rectangular  Com- 
partments UPON  the  Plan. 

GROINED  ARCHES  SPRINGING  FROM  POLYGONAL  PILLARS. 

To  execute  a ribbed -groined  ceiling  in  severies,  upon  a rectangular  plan,  so 
that  the  ribs  may  spring  from  points  in  the  quadrantal  arc  of  a circle,  of  which 
the  centres  are  in  the  angular  points  of  the  plan,  and  to  terminate  in  a horizontal 
ridge  parallel  to  the  sides  of  the  severies,  and  in  a vertical  plane,  bisecting  each 
side  of  the  plan. 

Let  S T V W,  Plate  1,  be  a portion  of  the  plan  consisting  of  two 

severies,  S T U X,  X U V W,  the  points  S,  T,  U,  V,  W,  X,  being  the  points 
into  which  the  axes  of  the  pillars  are  projected. 

Bisect  V W by  the  perpendicular  r L,  and  bisect  V U by  the  perpendicular 
p L.  Draw  the  straight  lines  uq,  vh,  lo  m,  x n,  y o,  radiating  from  V to  meet 
the  ridge  lines  r L and  L p in  the  points  r,  q,  L,  m,  n,  o,  and  the  arc  t z,  de- 
scribed from  V in  the  points  v,  v,  w,  x,  y,  and  these  lines  will  be  the  plans  of 
the  ribs  for  one  quarter  of  a severy. 

Suppose  now  the  rib  over  ^ r to  be  given,  and  let  this  rib  be  fig.  2,  which  is 
here  made  double.  The  half  ab  c is  the  rib  which  stands  upon  r t,  the  curve 

b c,fig.  2,  and  the  plans,  t r,  u q,  vL,  wm,  x n,  y o,  zp,  fig.  1,  of  the  ribs  are 

given  by  the  architect  in  the  plan  and  sections  of  the  work ; it  is  the  workman’s 
province  to  find  the  curvature  of  the  ribs,  and  the  formation  of  the  stones  for  the 
ceiling. 

For  this  purpose,  we  shall  suppose  that  the  chords  which  are  formed  by  the 
joints  in  the  intrados  upon  the  meeting  of  the  rib  over  t r to  be  equal ; therefore, 
divide  the  curve  be, fig.  2,  into  equal  parts,  so  as  to  admit  of  vault-stones  of  a 
convenient  size. 

From  the  points  1,  2,  3,  &zc.,fig.  2,  in  the  arc  b c,  draw  lines  perpendicular  to 
ab,  the  base  of  the  rib.  Transfer  the  parts  of  the  line  ab  to  ri,  fig.  1,  and  let 
A be  one  of  the  points  representing  e,fig.  3.  In  fig.  1,  draw  u t,  and  produce 
u t and  L r to  meet  each  other  in  the  point  3.  Draw  the  straight  line  A B 
radiating  to  the  point  2,  to  meet  the  plan  u q in  B.  Join  u v,  and  produce  v u 
and  L r to  meet  in  3,  and  draw  the  straight  line  B C radiating  from  2,  to  meet 
the  plan  y L in  C.  Join  viv,  and  produce  v w and  Lp  to  meet  each  other  in 

H.  Draw  C D radiating  to  the  point  H,  to  meet  iv  m in  D.  Join  ic  x,  and  pro- 

duce 10  X and  L p to  meet  each  other  in  1,  and  draw  D E radiating  to  the  point 

I,  to  meet  x n in  E.  Find  the  points  F and  G in  the  same  manner  as  each  of 


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CONSTRUCTION  OF  STONES  FOR  GOTHIC  VAULTS.  153 


the  points  B,  C,  D,  E,  have  been  found,  and  the  compound  line  AB  C DE  F G 
will  be  the  line  of  joints  corresponding  to  the  point  5,  fig.  2.  Find  the  lines  cor- 
responding to  the  other  joints  in  the  same  manner.  Transfer  the  divisions  in  the 
line  u q to  the  base  hne  of  Jig.  3,  and  draw  lines  perpendicular  to  the  base  as  or- 
dinates. Transfer  the  ordinates  oi  fig.  2 to  their  corresponding  ordinate  fig.  3, 
and  draw  the  curves  which  will  complete  the  inner  edge  of  the  rib,  fig.  3.  In 
the  same  manner  find  the  curve  of  the  ribs.  Jigs.  4,  5,  6,  &c.,  which  stand  over 
the  lines  v L,  icm,  x n,  6cc. 

Fig.  7 exhibits  a part  of  the  plan  of  a groin-ceiling,  consisting  of  two  severies 
when  the  plans  of  the  piers  are  squares,  of  which  the  angular  points  terminate  in 
the  sides  of  the  plan  of  each  severy,  and  then  we  have  only  to  find  the  diagonal 
ribs  and  those  upon  the  narrow  side  of  the  severy.  It  must,  however,  be  observ- 
ed, both  in  Jigs.  1 and  7,  that  only  one  of  the  curves  which  belong  to  arches  of 
the  two  sides  of  a severy  can  be  given  ; the  other  must  be  found  in  the  same 
manner  as  the  curves  of  the  intermediate  ribs.  In  Jig.  7 the  plan  of  the  joints 
has  only  two  points  of  convergence,  which  are  found  by  producing  the  side  of 
the  square  which  forms  the  plan  of  the  pillars,  and  the  plan  of  the  ridge-lines,  till 
they  meet  each  other. 

W'e  shall  now  proceed  towards  the  formation  of  the  stones  of  the  vaulting. 

Plate  XXL,  Fig.  2.  Let  A B C 1)  be  the  plan  of  one  cjuarter  of  a severy,  and 
let  li  C and  i f be  the  seats  of  two  adjacent  ribs,  and  let  h ij  j N C be  the  rib 
which  stands  upon  h C,  and  let  k I in  n be  the  plan  of  the  soffit  of  a stone.  Per- 
pendicular to  It  C draw  k ij  and  I J,  and  draw  y g pai'allel  to  h C.  Produce  n k to 
sand  nin  too.  Draw  / 1>  and  Is  respectively  parallel  to  sn  and  n m.  Draw 
Ir  perpendicular  to  Is;  make  Ir  equal  to  gj  and  join  s r.  Draw  lu  per- 
pendicular to  sn  ; and  from  s,  with  the  radius  si’,  describe  an  arc  meeting  lu 
in  the  point  u.  Draw  u v and  n v respectively  parallel  to  s n and  s u.  Perpen- 
dicular to  11  0 draw  o q and  in  p.  IMake  o q and  in  p each  equal  to  gJ,  and 
join  11  p and  n q.  Draw  p t perpendicular  to  n q,  meeting  n q in  the  point  t.  To 
form  the  winding  surface  of  the  inti-ados,  first  work  the  soffit  as  a plane  surface; 
on  the  plane  surface  describe  the  figure  u s ii  v.  Make  n w equal  to  ii  t. 

In  Jig.  3 make  the  angle  ab  c equal  to  s n o,  Jig.  2,  and  make  the  angle  c b e,Jig. 
3,  equal  to  o ii  q.  Having  the  two  legs  cba,  c b e,  of  a right-angled  trehedral,  find 
the  angle  g h i,  which  the  hypothenuse  makes  with  the  leg  c b e.  Secondly,  form 
the  bed  of  the  stone  to  make  an  angle  at  the  arris-line  n v with  the  surface  usn  v, 
equal  to  the  angle  g hi,  Jig.  3.  Draw  ic  x upon  the  end  of  the  stone  thus  formed 
perpendicular  to  n w,  and  make  w x equal  to  t p,  and  on  the  end  of  the  stone  draw 
11  X.  Join  k u ; then  the  four  points  n,  k,  u,  x,  are  the  four  angular  points  of  the 

20 


154 


PRACTICAL  MASONRY. 


soffit  of  the  stone.  The  other  end  of  the  stone  will  be  formed  in  a similar 
manner. 

On  the  nature  and  construction  of  Gothic  ceilings. 

Let  A,  B,  C,  D,  Plate  XXL,  fig.  1 , be  the  springing-points,  A C and  B D the 
plans  of  the  groins  disposed  in  the  vertices  of  the  angle  of  a rectangle,  their  planes 
bisecting  each  other  in  the  point  e ; also  let  Q U and  S X,  passing  through  the 
point  e,  and  bisecting  the  angles  A e B,  B e C,  C e D,  D e A,  be  the  plans  of  the 
ridges  of  the  Gothic  arches,  and  let  A E,  A H,  B J,  B K,  C M,  C N,  D P,  D G,  be 
the  springing-lines  of  the  Gothic  ceiling. 

Moreover,  let  the  four  straight  lines  E G,  H J,  K M,  N P,  at  right  angles  to 
Q U and  S X,  be  the  plans  of  four  right  sections  to  each  wing  of  the  groined 
vault. 

From  the  point  A:  as  a centre,  with  the  radius  kp,  describe  the  arc  hg ; and 
let  the  springing-lines  A E,  D G,  A H,  J B,  &c.,  be  such  as  to  meet  respectively 
in  the  points  Q,  S,  &c. 

To  construct  the  ribs  w'hich  are  at  right  angles  to  the  ridge-lines,  and  of  which 
their  plans  are  E G,  H J,  &c.  Let  us  suppose  that  the  given  rib  is  E F G,  standing 
upon  E G as  its  plan.  Prolong  A E and  D G to  meet  each  other  in  the  point  Q. 
Divide  the  half-curve  E F of  the  arch  into  as  many  equal  parts  as  the  number  of 
courses  is  intended  to  be  in  the  ceiling  on  each  side  of  the  ridge-line  of  the  in- 
trados  of  the  arch ; let  us  suppose  that  this  number  is  six,  and  that  h is  the  first 
point  of  division  from  the  bottom  point  E of  the  rib,  the  succession  of  parts  being 
E h,  hi,  &c.  From  the  points  h,  i,  &c.,  draw  the  straight  lines  hp,  i q,  &lc.,  per- 
pendicularly to  E G,  meeting  E G in  the  points  p,  q,  &c.  Through  the  joints 
p,  q,  &LC.,  draw  from  the  point  Q the  lines  Q r,  Q s,  &c.,  meeting  A C,  the  plan 
of  the  groin,  in  the  points  r,  s,  &c.,  and  perpendicularly  to  A C draw  the  straight 
lines  7'j,  s k,  Slc.  Make  ?'j,  s k,  &c.,  each  respectively  equal  to  ph,  q i,  &cc. ; 
through  the  points  A,j,  k,  &c.,  draw  the  curve  Aj  k V for  one  half  of  the  curve 
of  the  groin  rib  ; the  other  half  is  symmetrical,  and  therefore  the  same  curve  in  a 
reversed  order. 

To  find  the  rib  H I J.  Prolong  A H and  B J to  meet  each  other  in  the  point  S, 
and  draw  the  lines  r S,  s S,  &c.,  intersecting  H J in  the  points  t,  u,  &c.  Draw 
t n,  ii  0,  &LC.,  perpendicular  to  H J,  and  make  tn,  uo,  &lc.,  respectively  equal  to 
p h,  qi,'&LC.  Through  the  points  H,  n,  o,  &c.,  draw  the  curve  H I,  and  H I will 
be  the  curve  of  one  half  of  the  arch  over  the  line  H J for  the  plan. 

Hence  we  see  that  the  lines  y h,  k i,  &c.,  prolonged,  will  meet  the  line  Q R per- 
pendicular to  the  plane  A B C D in  the  points  f,  g,  &.C.,  at  the  same  heights,  Q/, 
Q^,  &c.,  as  p h,  p i,  &c.,  of  the  heights  of  the  ordinates  of  the  given  rib.  Since 
both  sides  are  symmetrical,  one  description  will  serve  each  of  them. 


CONSTRUCTION  OF  STONES  FOR  GOTHIC  VAULTS.  155 


To  describe  a Gothic  isosceles  arch  to  any  width,  height,  and  to  a given  verti- 
cal angle. 

Plate  XX.  Let  AB,  fig.  1,  be  the  span  or  width  of  the  arch  ; m C,  perpen- 
dicular to  A B,  from  the  middle  point  m,  the  height ; and  eCf  the  vertical  angle 
given  by  the  tangents  C e and  C fi  making  equal  angles  with  the  line  of  height, 
m C. 


In  this  example,  the  points  e and  /,  the  lower  extremities  of  the  tangents,  are 
regulated  by  erecting  A e and  B /,  each  perpendicular  to  A B,  and  making  each 
equal  to  three  fourths  of  the  height-line,  m C. 

From  the  point  A,  towards  B,  make  A k equal  to  A e or  B/,  that  is,  equal  to 
three  fourths  m C ; and  from  the  point  C,  the  vertex  of  the  arch,  draw  C e per- 
pendicular to  CL  In  C i take  C /,  equal  to  A k,  and  join  kl ; bisect  klhy  a.  per- 
pendicular, d i meeting  C i in  the  point  i ; join  i k,  and  produce  i k to  g. 

From  the  point  i,  with  the  radius  i C,  describe  an  arc  C g,  meeting  the  line  ig 
in  the  point  g,  and  from  the  point  k,  with  the  radius  kg,  describe  an  arc  g A,  and 
A g C will  be  the  one  half  of  the  intrados  of  the  Gothic  arch  required. 

Produce  C m to  meet  A:  i in  the  point  n,  and  in  A B make  m u equal  to  m k, 
join  n u,  and  prolong  nu  to  t,  and  u n to  o.  Make  n o equal  to  n L From  the 
centre  o,  with  the  radius  o C,  describe  the  arc  C h,  meeting  ut  in  the  point  h,  and 
from  u,  with  the  radius  u h,  describe  the  arc  h B,  and  BAG  will  be  the  other  half 
of  the  intrados. 

Upon  A B,  prolonged  both  ways  to  p and  s,  make  Ap  and  B s each  equal  toi 
the  length  of  each  one  of  the  arch-stones  in  a direction  of  a radius.  \ 

From  the  point  A:  as  a centre,  with  the  radius  kp,  describe  the  arc  p g,  and 
from  the  point  i,  with  the  radius  ig,  describe  the  arc  gi',  and  pgr  will  be  half  of 
the  extrados  of  the  arch. 

In  the  same  manner  will  be  formed  str,  the  other  half  of  the  extrados.  The 
arch- stones  are  divided  upon  the  dotted  line  in  the  middle  into  equal  parts,  and 
the  point  lines  are  drawn  by  the  centres  of  the  intrados  and  extrados  of  the  arch. 


% 


REMARK.  • 


When  the  height  of  the  arch  is  equal  to  or  greater  than  half  the  span,  and 
when  it  is  not  necessary  that  the  vertical  angle  should  be  given,  the  curves  of  the 
intrados  and  extrados  on  the  one  side  may  be  described  from  the  same  centre,  as 
also  those  of  the  other  side  from  another  centre. 

The  most  easy  Gothic  arch  to  describe  is  that  of  which  the  height  of  the  intra- 
dos is  such  as  to  be  the  perpendicular  of  an  equilateral  triangle,  described  upon 
the  spanning-line  as  a base ; such  is  fig.  2,  and  these  centres  are  the  points  to 
which  the  radiating  joints  must  tend. 


156 


PRACTICAL  MASONRY. 


Gothic  arches  seldom  exceed  in  height  the  perpendicular  of  the  equilateral 
triangle  inscribed  in  the  intrados  of  the  aperture  ; but  when  the  arch  is  surmount- 
ed, and  the  height  less  than  the  perpendicular  of  the  equilateral  triangle  made 
upon  the  base,  draw  a straight  line  from  one  extremity  of  the  base  to  the  vertex, 
and  bisect  this  line  by  a perpendicular.  From  the  point  where  the  perpendicu- 
lar meets  the  base  of  the  arch,  and  with  a radius  equal  to  the  distance  between 
this  point  and  the  extremity  of  the  base  joined  to  the  vertex,  describe  an  arc 
between  the  two  points,  joined  by  the  straight  line,  and  the  curve  which  forms 
one  side  of  the  intrados  will  be  complete.  In  the  same  manner  will  be  formed 
the  curve  on  the  other  side  (see  fig.  3),  so  that  by  only  two  centres  the  whole  of 
the  intrados  will  be  formed. 

Figs.  4 and  5 show  the  method  of  erecting  another  form  of  Gothic  arches. 

Fig.  4 represents  the  manner  of  inserting  the  stone  in  a straight  wall,  so  as  to 
form  a circular  pointed  arch. 

Fig.  5 shows  the  manner  of  forming  the  same  arch.  Let  B C be  the  base-line 
of  the  arch  ; find  the  centre  A,  of  B C ; at  A erect  the  perpendicular  A D,  the 
intended  height  of  the  arch ; find  i,  the  centre  of  A D,  produce  A D to  a,  and 
make  A a equal  to  A i ,*  join  B D,  and  divide  it  into  five  equal  parts  at  1,  2,  3,  4,  5. 
Draw  the  line  a 2 through  the  point  e,  produce  a 2 to  g,  make  g 2 equal  to  a 2, 
and  e and  g will  be  the  radiating  points.  From  the  point  e,  with  the  radius  e B, 
describe  the  arc  B 2,  and  from  the  point  g,  with  the  radius  g D,  describe  the  arc 
D 2,  and  B 2 will  be  the  intrados  of  one  portion  of  the  arch,  and  D 2 the  extra- 
dos  of  the  other  corresponding  portion  of  the  arch.  The  extrados  and  intrados 
of  the  remaining  side  may  be  found  in  the  same  manner. 


ON  ANCIENT  WALLS. 


157 


CHAPTER  V. 

SECTION  I. — Ancient  Walls. 

The  ancients  used  several  kinds  of  walls,  in  which  more  or  less  masonry  was 
always  introduced.  They  had  their  incertain,  or  inserted  walls,  and  also  their  re- 
ticulated walls. 

The  uncertain  or  irregular  walls  are  those  where  the  stones  are  laid  with  their 
natural  dimensions,  and  their  figure  and  size  of  course  uncertain.  Plate  XXII., 
fig.  2.  The  materials  rest  firmly  one  upon  another,  and  are  interwoven  together, 
so  that  they  are  much  stronger  than  the  reticulated,  though  not  so  handsome. 
In  this  kind  of  wall  the  courses  were  always  level;  but  the  upright  joints  were 
not  ranged  regularly  or  perpendicularly  to  each  other  in  alternate  courses,  nor  in 
any  other  respect  correspondently ; but  uncertainly,  according  to  the  size  of  the 
bricks  or  stones  employed.  Thus  our  bricks  are  arranged  in  ordinary  walls,  in 
which  all  that  is  regarded  is,  that  the  upright  joints  in  two  adjoining  courses  do 
not  coincide.  Walls  of  both  sorts  are  formed  of  very  small  pieces,  that  they  may 
have  a sufficiency  of,  or  be  saturated  with,  mortar,  which  adds  greatly  to  their 
solidity. 

To  saturate  or  fill  up  a wall  with  mortar,  is  a practice  which  ought  to  be  had 
recourse  to  in  every  case  where  small  stones  or  bricks  admit  of  it.  It  consists  in 
mixing  fresh  lime  with  water,  and  pouring  it,  while  hot,  among  the  masonry  in 
the  body  of  the  wall. 

The  walls  called  by  the  Greeks  isidomum,  fig.  3,  are  those  in  which  all  the 
courses  are  of  equal  thickness ; and  pscudo-isidomum,  or  false,  fig.  4,  when  the 
courses  are  unequal.  Both  these  walls  are  firm  in  proportion  to  the  compactness 
of  the  mass,  and  the  solid  nature  of  the  stones,  so  that  they  do  not  absorb  the 
moistness  of  the  mortar ; and,  being  situated  in  regular  and  level  courses,  the 
mortar  is  prevented  from  falling,  and  thus  the  whole  thickness  of  the  wall  is 
united.  In  the  wall  called  complecton,  fig.  1,  the  faces  of  the  stones  are  smooth, 
the  other  sides  being  left  as  they  came  from  the  quarry,  and  are  secured  with 
alternate  joints  and  mortar ; the  face  of  this  wall  was  often  covered  with  a coat  of 
plaster.  This  kind  of  building,  called  diamixton,  fig.  5,  admits  of  great  expedi- 
tion, as  the  artificer  can  easily  raise  a case  or  shell  for  the  two  faces  of  the  work, 
and  fill  the  intermediate  space  with  rubble- work  and  mortar.  Walls  of  this  kind, 
consequently,  consist  of  three  coats  ; two  being  the  faces  and  one  the  rubble 
core,  which  is  the  middle ; but  the  great  works  of  the  Greeks  were  not  thus  built. 


158 


PRACTICAL  MASONRY. 


for  in  them  the  whole  intermediate  space  between  the  two  faces  was  constructed 
in  the  same  manner  as  the  faces  themselves;  and  they  besides  occasionally  intro- 
duced diatonos,  or  single  pieces,  extending  from  one  face  to  the  other,  to 
strengthen  and  bind  the  wall,  Jig.  5,  a a.  These  different  methods  of  uniting  the 
several  parts  of  the  masonry  of  a wall  should  be  well  considered  by  all  persons, 
who  are  intrusted  with  works  requiring  great  strength  and  durability. 

If  the  walls  are  isidomoi,  and  fastened  together  with  iron,  they  are  properly 
called  cramped,  fig.  5,  c c c.  The  net-work  structure,  fig.  6,  was  much  used  in 
ancient  Rome,  and  is  beautiful  to  the  sight,  but  is  liable  to  crack,  wherefore  no 
ancient  specimens  of  this  kind  remain.  Plate  XXl\.,fig.  7,  exhibits  a species  of 
ancient  wall  which  may  be  seen  at  Naples.  There  are  two  walls,  A A,  of  square 
stones,  four  feet  thick  ; their  distance  six  feet.  They  are  bound  together  by  the 
transverse  walls  B B,  at  the  same  distance.  The  cavity  C C,  left  between, 
s six  feet  square,  and  is  filled  up  with  rubble-stones  and  earth. 

Fig.  8 represents  a second  kind,  built  of  square  stones ; this  was  called 
pseitdo-isidomiim,  D D ; to  be  seen  now  at  Rome  in  the  Temple  of  Augustus.  The 
third  species  is  the  uncertain,  fig.  9 ; a specimen  of  which  still  remains  at  Pales- 
trina, twenty  miles  east  of  Rome.  Another  kind,  10,  which  may  be  seen  at 
Sermione,  upon  the  Lake  of  Garda,  is  a species  of  w ooden  wall,  E E,  and  is  called 
formcc  ; it  is  stuffed  with  stone,  mortar,  See.,  at  random.  The  planks  being  taken 
away,  the  wall  E E appears,  and  is  called  formaceous. 

The  fifth  kind.  Jig.  11,  are  walls  made  of  cement,  G G,  composed  of  rough 
pebbles  out  of  a river  or  from  a rock ; sometimes  of  shell,  as  are  the  walls  of 
Turin  in  Piedmont.  'Phis  kind  of  wall  should  be  bound  by  three  courses  of 
bricks,  at  the  height  of  two  feet,  as  H H. 

The  sixth  kind  is  brick-work.  Jig.  12,  which,  especially  in  the  walls  of  a city, 
or  extraordinary  building,  is  constructed  like  the  diamixton,{ov  the  bricks  appear, 

1 1,  and  the  rubbish  lies  concealed  in  the  middle,  K K.  In  the  bottom  there  are 
six  courses  of  larger  bricks  ; then  some  less,  at  the  height  of  three  feet ; then 
the  walls  are  bound  again  with  three  courses  of  larger  bricks ; an  example  of  this 
kind  still  remains  in  the  Pantheon,  and  in  the  hot-baths  built  by  Diocletian. 

The  seventh  kind,yf^.  13,  is  net-work,  L L,  which  Palladio  did  not  approve 
of,  and  to  insure  the  strength  of  which  he  proposed  to  erect  buttresses  at  the 
angles  M M,  and  to  place  transversely,  or  lengthwise,  six  courses  of  bricks  at  the 
bottom,  N N,  and  in  the  middle  three  courses,  O O,  whenever  the  net-work  is 
raised  six  feet. 

The  existing  examples  of  Roman  complecton,  with  partial  cores  of  rubble-work 
or  brick,  sufficiently  prove  its  durability ; but  that  of  the  Greeks  was  worked 
throughout  the  whole  thickness  of  the  wall  in  the  same  manner  as  the  facing  of 
the  fronts,  as  their  temples  now  existing  testify. 


CONSTRUCTION  OF  BRICK  ARCHES. 


159 


The  thickness  of  walls  should  be  regulated  according  to  the  nature  of  the  ma- 
terials, and  the  magnitude  of  the  edifice.  Walls  of  stone  may  be  made  one  fifth 
thinner  than  those  of  brick;  and  brick  walls  in  the  basement  and  ground  stories 
of  buildings  of  the  first  rate  should  be  reticulated  with  stones,  to  prevent  their 
splitting  ; a circumstance  which  has  been  too  much  disregarded  by  our  builders. 


SECTION  II.  — Construction  of  Brick  Arches. 

Plate  XXIII.,  fig.  1,  represents  a straight  arch  or  aperture  in  a brick  wall. 
Describe  an  isosceles  triangle  on  C D,  the  width  of  the  arch,  as  a base-line,  whose 
vertex  will  be  at  a,  produce  a C to  E,  and  a D to  F,  and  E F will  be  the  extra- 
dos,  and  C D the  intrados  of  the  arch. 

Divide  C D and  E F into  the  same  number  of  equal  parts,  and  make  the  bricks 
to  correspond  with  these  parts. 

Fig.  2 is  a segment  arch.  Describe  an  isosceles  triangle  as  in  fig.  1,  and 
bisect  C D in  6 ; from  the  point  a,  with  the  radius  a D,  describe  the  arc  D 6 C, 
and  with  the  radius  a C,  produced  from  the  point  a,  describe  the  extrados,  and 
C 6 D will  be  the  intrados  of  the  arch. 

Fig.  5 is  a semicircular  arch  ; the  intrados  of  which  is  easily  found  by  making 
the  semidiameter,  or  one  half  the  width  of  the  arch,  the  radius  of  the  semicircle 
beD. 

Fig.  4 is  a semi-elliptical  arch,  formed  from  three  points.  Divide  D d,  the  width 
of  the  arch,  into  three  equal  parts  at  the  points  B,  b;  from  the  centre  A of  D d, 
erect  the  perpendicular  Ae,  and  produce  A e at  pleasure;  join  B a,  making  B a 
equal  to  A D ; produce  a B to  c ; at  the  point  B,  with  the  radius  B c,  describe  the 
arc  e d ; join  b a,  and  produce  ba  to  C ; then,  with  the  radius  a c,  at  the  point  a, 
describe  the  arc  ceC\  and  at  the  point  6,  with  the  radius  b d,  describe  the  arc  C d, 
and  D e d,  the  intrados  of  the  intended  arch,  will  be  complete. 

Figs.  3 and  6 show  the  construction  of  Gothic  arches  on  the  principles  laid 
down  in  Plate  XXXlll.,  figs.  1 and  3. 

Nos.  1 and  2 represent  the  application  of  inverted  arches  to  the  foundations  of 
brick  wall.  (See  Foundations.) 


SECTION  III.  — Bricklaying. 


Bricklaying  is  the  art  of  building  with  bricks,  or  the  uniting  them,  by  cement 
or  mortar,  into  various  forms  for  particular  purposes. 


160 


PRACTICAL  MASONRY. 


Bricks  are  laid  in  a varied  but  regular  form  of  connection,  or  bond,  as  exhibited 
in  Plate  XXIII.  The  mode  of  laying  them  for  an  eight-inch  walling  shown  in 
fig.  7 being  denominated  English  bond,  and  fig.  8,  Flemish  bond.  Fig.  9 is 
English  bond  in  a brick-and-a-half  or  twelve-inch  walling;  and  fig.  10,  Flemish 
bond  in  the  same.  Fig.  11  represents  another  method  of  disposing  Flemish 
bond  in  a twelve-inch  wall.  Fig.  12,  English  bond  in  a sixteen-inch,  or  a two- 
brick-thick  wall ; and  fig.  13,  English  bond  in  a two-and-a-half-brick-thick  wall. 

Fig.  16  is  another  brick  bond,  which  is  admired  for  its  regularity  and  strength; 
it  is  formed  of  brick  and  tiles,  and  connected  with  this  fig.  is  the  next  course 
above  the  tiles,  composed  of  headers. 

Figs.  14,  15,  17,  and  20,  represent  square  courses,  in  pairs,  of  Flemish  bond. 
In  each  pair,  if  one  be  the  lower  course,  the  other  will  be  the  upper  course. 

The  bricks  having  their  lengths  in  the  thickness  of  the  wall  are  termed  head- 
ers, and  those  which  have  their  lengths  in  the  length  of  the  wall  are  stretchers. 
By  a course  in  walling  is  meant  the  bricks  contained  between  two  planes  parallel 
to  the  horizon,  and  terminated  by  the  faces  of  the  wall.  The  thickness  is  that 
of  one  brick  with  mortar.  The  mass  formed  by  bricks  laid  in  concentric  order, 
for  arches  or  vaults,  is  also  denominated  a course. 

The  disposition  of  bricks  in' a wall,  of  which  every  alternate  course  consists  of 
headers,  and  of  which  every  course  between  every  two  nearest  courses  of  head- 
ers consists  of  stretchers,  constitutes  English  bond. 

The  disposition  of  bricks  in  a wall  (except  at  the  quoins)  of  which  every  alter- 
nate brick  in  the  same  course  is  a header,  and  of  which  every  brick  between 
every  two  nearest  headers  is  a stretcher,  constitutes  Flemish  bond. 

It  is,  therefore,  to  be  understood  that  English  bond  is  a continuation  of  one  kind, 
throughout,  in  the  same  course  or  horizontal  layer,  and  consists  of  alternate  lay- 
ers of  headers  and  stretchers,  as  shown  in  the  plate ; the  headers  serving  to  bind 
the  wall  together  in  a longitudinal  direction,  or  lengthwise,  and  the  stretchers  to 
prevent  the  wall  splitting  crosswise  or  in  a transverse  direction.  Of  these  evils 
the  first  is  the  worst,  and  therefore  the  most  to  be  feared. 

It  is  supposed  that  the  old  English  mode  of  brick-work  affords  the  best  securi- 
ty against  such  accidents,  as  work  of  this  kind,  wheresoever  it  is  so  much  under- 
mined as  to  cause  a fracture,  is  not  subject  to  such  accidents,  but  separates,  if  at 
all,  by  breaking  through  the  solid  brick,  just  as  if  the  wall  were  composed  of  one 
piece. 

The  ancient  brick-work  of  the  Romans  was  of  this  kind  of  bond,  but  the  ex- 
isting specimens  are  very  thick,  and  have  three,  or  sometimes  more,  courses  of 
brick  laid  at  certain  intervals  of  the  height,  stretchers  on  stretchers,  and  headers 
on  headers,  opposite  the  return  wall,  and  sometimes  at  certain  distances  in  the 


ON  BRICKLAYING. 


161 


length,  forming  piers,  that  bind  the  wall  together  in  a transverse  direction ; the 
intervals  between  these  piers  were  filled  up,  and  formed  panels  of  rubble  or  retic- 
ulated work ; consequently  great  substance,  with  strength,  were  economically  ob- 
tained. 

It  will  also  be  understood,  Flemish  bond  consists  in  placing,  in  the  same  course, 
alternate  headers  and  stretchers  ; a disposition  considered  as  decidedly  inferior  in 
every  thing  but  appearance,  and  even  in  this  the  difference  is  trifling ; yet  to  ob- 
tain it  strength  is  sacrificed,  and  bricks  of  two  qualities  are  fabricated  for  the  pur- 
pose ; a firm  brick  often  rubbed,  and  laid  in  what  the  workmen  term  a putty -joint, 
for  the  exterior,  and  an  inferior  brick  for  the  interior,  substance  of  the  wall ; but, 
as  these  did  not  correspond  in  thickness,  the  exterior  and  interior  surface  of  the 
wall  would  not  be  otherwise  connected  together  than  by  an  outside  heading 
brick,  here  and  there  continued  of  its  whole  length ; but,  as  the  work  does  not 
admit  of  this  at  all  times,  fiom  the  want  of  agreement  in  the  exterior  and  interior 
courses,  these  headers  can  be  introduced  only  where  such  a correspondence 
takes  place,  which,  sometimes,  may  not  occur  for  a considerable  space. 

Walls  of  this  kind  consist  of  two  faces  of  four-inch  work,  with  very  little  to 
connect  them  together,  and,  what  is  still  worse,  the  interior  face  often  consists  of 
bad  brick,  little  better  than  rubbish.  The  practice  of  Flemish  bond  has,  notwith- 
standing, continued  in  England,  from  the  time  of  William  and  Mary,  when  it  was 
introduced,  with  many  other  Dutch  fashions,  and  the  workmen  are  so  infatuated 
with  it,  that  there  is  now  scarcely  an  instance  of  the  old  English  bond  to  be 
seen. 

The  frequent  splitting  of  Myalls  into  two  thicknesses  has  been  attributed  to  the 
Flemish  bond  alone,  and  various  methods  have  been  adopted  for  its  prevention. 
Some  have  laid  laths,  or  slips  of  hoop-iron,  occasionally,  in  the  horizontal  points 
between  the  two  courses ; others  have  laid  diagonal  courses  of  bricks  at  certain 
heights  from  each  other ; but  the  effect  of  the  last  method  is  questionable,  as  in 
the  diagonal  course,  by  their  not  being  continued  to  the  outside,  the  bricks  are 
much  broken  where  the  strength  is  required. 

The  outer  appearance  is  all  that  can  be  urged  in  favor  of  Flemish  bond,  and 
many  are  of  opinion,  that,  were  the  English  mode  executed  with  the  same  at- 
tention and  neatness  that  is  bestowed  on  the  Flemish,  it  would  be  considered  as 
equally  handsome  ; and  its  adoption,  in  preference,  has  been  strenuously  recom- 
mended. 

In  forming  English  bond,  the  following  rules  are  to  be  observed. 

1st.  Each  course  is  to  be  formed  of  headers  and  stretchers  alternately,  as 

2d.  Every  brick  in  the  same  course  must  be  laid  in  the  same  direction ; but  in 

21 


162 


PRACTICAL  MASONRY. 


no  instance  is  a brick  to  be  placed  with  its  whole  length  along  the  side  of  another ; 
but  to  be  so  situated  that  the  end  of  one  may  reach  to  the  middle  of  the  others 
which  lie  contiguous  to  it,  excepting  the  outside  of  the  stretching  course,  where 
three-quarter  bricks  necessarily  occur  at  the  ends,  to  prevent  a continual  upright 
joint  in  the  face-work. 

3d.  A wall,  which  crosses  at  a right  angle  with  another,  will  have  all  the  bricks 
of  the  same  level  course  in  the  same  parallel  direction,  which  completely  binds 
the  angles,  as  shown  by  Jigs.  7,  9,  and  12,  Plate  XXIII. 

Figs.  14,  15,  17,  and  20,  are  the  method  of  forming  square  pier,  as  shown  by 
two  courses,  one  laid  on  top  of  the  other. 

Fig.  1 1,  a pair  of  courses  in  the  English  bond,  of  one  foot  four  inches  square, 
or  the  length  of  two  bricks. 

Figs.  15,  17,  and  20,  are  square  piers  in  the  Flemish  bond  ; 20  is  two  and  a 
half  brick  square  ; 15  is  a pier  of  three  bricks  in  length  to  one  side  ; 15  is  a pier 
of  the  length  of  three  and  a half  brick  square ; 1 7 the  length  of  two  bricks  square ; 
1 4 is  a pier  of  three  length  square. 

The  great  principle  in  the  practice  of  brick-work  lies  in  the  proclivity  or  cer- 
tain motion  of  absolute  gravity,  caused  by  a quantity  or  multiplicity  of  substances 
being  added  or  fixed  in  resistible  matter,  and  which,  therefore,  naturally  tends 
downwards,  according  to  the  weight  and  power  impressed.  In  bricklaying,  this 
proclivity,  chiefly  by  the  yielding  mixture  of  the  matter  of  which  mortar  is  com- 
posed, cannot  be  exactly  calculated ; because  the  weight  of  a brick,  or  any  other 
substance  laid  in  mortar,  will  naturally  decline  according  to  its  substance  or  qual- 
ity ; particular  care  should  be  taken,  therefore,  that  the  material  be  of  one  regu- 
lar and  equal  quality  all  through  the  building  ; and  likewise,  that  the  same  force 
should  be  used  to  one  brick  as  to  another ; that  is  to  say,  the  stroke  of  the 
trowel,  a thing  or  point  in  practice  of  much  more  consequence  than  is  generally 
imagined  ; for  if  a brick  be  actuated  by  a blow,  this  will  be  a much  greater 
pressure  upon  it  than  the  weight  of  twenty  bricks.  It  is,  also,  especially  to  be 
remarked,  that  the  many  bad  effects  arising  from  mortar  not  being  of  a proper 
quality  should  make  masters  very  cautious  in  the  preparation  of  it,  as  well  as  the 
certain  quality  of  materials  of  which  it  is  composed,  so  that  the  whole  structure 
may  be  of  equal  density,  as  nearly  as  can  be  effected. 

Here  we  may  notice  a particular  which  often  causes  a bulging  in  large  flank 
walls,  especially  when  they  are  not  properly  set  off  on  both  sides  ; that  is,  the 
irregular  method  of  laying  bricks  too  high  on  the  front  side ; this,  and  building 
the  walls  too  high  on  one  side,  without  continuing  the  other,  often  causes  defects. 
Notwithstanding,  of  the  two  evils,  this  is  the  least ; and  bricks  should  incline 
rather  to  the  middle  of  the  wall,  that  one  half  of  the  wall  may  act  as  a shore  to 


ON  BEICKLAYING. 


163 


the  other.  But  even  this  method,  carried  too  far,  will  be  more  injurious  than 
beneficial,  because  the  full  width  of  the  wall,  in  this  case,  does  not  take  its  abso- 
lute weight,  and  the  gravity  is  removed  from  its  first  line  of  direction,  which,  in 
all  walls,  should  be  perpendicular  and  united ; and  it  is  further  to  be  considered, 
that,  as  the  walls  will  have  a superincumbent  weight  to  bear,  adequate  to  their 
full  strength,  a disjunctive  digression  is  made  from  the  right  line  of  direction  ; 
the  conjunctive  strength  becomes  divided ; and  instead  of  the  whole  or  united 
support  from  the  wall,  its  strength  is  separated  in  the  middle,  and  takes  two  later- 
al bearings  of  gravity,  each  insufficient  for  the  purpose ; therefore,  like  a man 
overloaded  either  upon  his  head  or  shoulders,  naturally  bends  and  stoops  to  the 
force  impressed ; in  which  mutable  state  the  grievances  above  noticed  usually 
occur. 

Another  great  defect  is  frequently  seen  in  the  fronts  of  houses,  in  some  of  the 
principal  ornaments  of  brick-work,  as  arches  over  windows,  &c.,  and  which  is  too 
often  caused  by  a want  of  experience  in  rubbing  the  bricks ; which  is  the  most 
difficult  part  of  the  branch,  and  ought  to  be  very  well  considered.  The  faults 
alluded  to  are  the  bulging  or  convexity  in  which  the  faces  of  arches  are  often 
found,  after  the  houses  are  finished,  and  sometimes  a looseness  in  the  key  or  cen- 
tre bond.  The  first  of  these  defects,  which  appears  to  be  caused  by  too  much 
weight,  is,  in  reality,  no  more  than  a fault  in  the  practice  of  rubbing  the*  bricks  too 
much  off  on  the  insides ; for  it  should  be  a standing  maxim  (if  you  expect  them 
to  appear  straight  under  their  proper  weight)  to  make  them  the  exact  gauge  on 
the  inside  that  they  bear  upon  the  front  edges ; by  which  means  their  geometri- 
cal bearings  are  united,  and  tend  to  one  centre  of  gravity. 

The  latter  observation,  of  camber  arches  not  being  skewed  enough,  is  an  egre- 
gious fault ; because  it  takes  greatly  from  the  beauty  of  the  arch,  and  renders  it 
insignificant.  The  proper  method  of  skewing  all  camber  arches  should  be  one 
third  of  their  height.  For  instance,  if  an  arch  is  nine  inches  high,  it  should  skew 
three  inches ; one  of  twelve  inches,  four ; one  of  fifteen,  five ; and  so  of  all  the 
numbers  between  those.  Observe,  in  dividing  the  arch,  that  the  quantity  con- 
sists of  an  odd  number ; by  so  doing,  you  will  have  proper  bond,  and  the  key 
bond  in  the  middle  of  the  arches ; in  which  state  it  must  always  be,  both  foi 
strength  and  beauty.  Likewise  observe,  that  arches  are  drawn  from  one  centre ; 
the  real  point  of  camber  arches  is  obtained  from  the  above  proportion.  First, 
divide  the  height  of  the  arch  mto  three  parts ; one  is  the  dimension  for  the  skew- 
ing ; a line  drawn  from  that  through  the  point  at  the  bottom  to  the  perpendicular 
of  the  middle  arch  gives  the  centre ; to  which  all  the  rest  must  be  drawn. 


164 


PRACTICAL  MASONRY. 


SECTION  IV.  — Foundations. 

RULES  TO  BE  OBSERVED  IN  LAYING  FOUNDATIONS. 

If  a projected  building  is  to  have  cellars,  under-ground  kitchens,  &c.,  there 
will  commonly  be  found  a sufficient  bottom,  without  any  extra  process,  for  a good 
solid  foundation.  When  this  is  not  the  case,  the  remedies  are  to  dig  deeper ; 
or  to  drive  in  large  stones  with  the  rammer ; or  by  laying  in  thick  pieces  of  oak, 
crossing  the  direction  of  the  wall,  and  planks  of  the  same  timber,  wider  than  the 
intended  wall,  and  running  in  the  same  direction  with  it.  The  last  one  to  be 
spiked  firmly  to  the  cross  pieces  to  prevent  their  sliding,  the  ground  having  been 
previously  well  rammed  under  them. 

The  mode  of  ascertaining  if  the  ground  be  solid  is  by  the  rammer ; if,  by  strik- 
ing the  ground  with  this  tool,  it  shake,  it  must  be  pierced  with  a borer,  such  as  is 
used  by  well-diggers ; and,  having  found  how  deep  the  firm  ground  is  below  the 
surface,  you  must  proceed  to  remove  the  loose  or  soft  part,  taking  care  to  leave  it 
in  the  form  of. steps  if  it  be  tapering,  that  the  stones  may  have  a solid  bearing,  and 
not  be  subject  to  slide,  which  would  be  likely  to  happen  if  the  ground  were  dug 
in  the  form  of  an  inclined  plane. 

If  the  ground  prove  variable,  and  be  hard  and  soft  at  different  places,  the  best 
way  is  to  turn  arches  from  one  hard  spot  to  another.  Inverted  arches  have  been 
used  for  this  purpose  with  great  success,  by  bringing  up  the  piers,  which  carry 
the  principal  weight  of  the  building,  to  the  intended  height  and  thickness,  and 
then  turning  reversed  arches  from  one  pier  to  another,  as  shown  in  figs.  3 and  6, 
Plate  XXIII.,  Nos.  1 and  2. 

In  this  case,  it  is  clear  that  the  piers  cannot  sink  without  carrying  the  arches,  and 
consequently  the  ground  on  which  they  lie,  with  them.  This  practice  is  excel- 
lent in  such  cases,  and  should  therefore  be  general,  wffierever  required. 

Where  the  hard  ground  is  to  be  found  under  the  apertures  only,  build  your  piers 
on  those  places,  and  turn  arches  from  one  to  the  other.  In  the  construction  of 
arches  some  attention  must  be  paid  to  the  breadth  of  the  insisting  pier,  whether  it 
will  cover  the  arch  or  not ; for,  suppose  the  middle  of  the  piers  to  rest  over  the  mid- 
dle of  the  summit  of  the  arches,  then  the  narrower  the  piers,  the  more  curvature 
the  supporting  arch  ought  to  have  at  the  apex.  When  arches  of  suspension  are 
used,  the  intrudes  ought  to  be  clear,  so  that  the  arch  may  have  the  full  ef- 
fect ; but,  as  already  noticed,  it  will  also  be  requisite  here  that  the  ground  on 
which  the  piers  are  erected  be  uniformly  hard ; for  it  is  better  that  it  should 
be  uniform,  though  not  so  hard  as  might  be  wished,  than  to  have  it  un- 


ON  WALLS. 


165 


equally  so  ; because,  in  the  first  case,  the  piers  would  descend  uniformly,  and  the 
building  remain  uninjured ; but,  in  the  second,  a vertical  fracture  would  take 
place,  and  endanger  the  whole  structure. 


SECTION  V.  — Walls,  &c. 

The  foundation  being  properly  prepared,  the  choice  of  materials  is  to  be  con- 
sidered. In  places  much  exposed  to  the  weather,  the  hardest  and  best  bricks 
must  be  used,  and  the  softer  reserved  for  in-door  work,  or  for  situations  less  ex- 
posed. 

If  laying  bricks  in  dry  weather,  and  the  work  is  required  to  be  firm,  wet  your 
bricks  by  dipping  them  in  water,  or  by  causing  water  to  be  thrown  over  them 
before  they  are  used.  Few  workmen  are  sufficiently  aware  of  the  advantage  of 
wetting  bricks ; but  experience  has  shown,  that  works  in  which  this  practice  has 
been  followed  have  been  much  stronger  than  others,  wherein  it  has  been  neglect- 
ed. It  is  particularly  serviceable  where  work  is  carried  up  thin,  and  putting 
in  grates,  furnaces,  &c. 

In  the  winter  season,  so  soon  as  frosty  and  stormy  weather  sets  in,  cover  your 
wall  with  straw  or  boards ; the  first  is  the  best,  if  well  secured,  as  it  protects  the 
top  of  the  wall,  in  some  measure,  from  frost,  which  is  very  prejudicial,  particular- 
ly when  it  succeeds  much  rain  ; for  the  rain  penetrates  to  the  heart  of  the  wall, 
and  the  frost,  by  converting  the  water  into  ice,  expands  it,  and  causes  the  mortar 
to  assume  a short  and  crumbly  nature,  and  altogether  destroys  its  tenacity. 

In  working  up  a wall,  it  is  proper  not  to  work  more  than  four  or  five  feet  at  a 
time ; for,  as  all  walls  shrink  immediately  after  building,  the  part  which  is  first 
brought  up  will  remain  stationary ; and  when  the  adjoining  part  is  raised  to  the 
same  height,  a shrinkage  or  settling  will  take  place,  and  separate  the  former  from 
the  latter,  causing  a crack,  which  will  become  more  and  more  evident  as  the 
work  proceeds. 

In  carrying  up  any  particular  part,  each  side  should  be  sloped  off,  to  receive  the 
bond  of  the  adjoining  work  on  the  right  and  left.  Nothing  but  absolute  necessity 
can  justify  carrying  the  work  higher,  in  any  particular  part,  than  one  scaffold  ; for> 
wherever  it  is  so  done,  the  w'orkmen  should  be  answerable  for  all  the  evil  that 
may  arise  from  it. 

The  distinctions  of  bond  have  already  been  shown,  and  we  shall  now  detail 
them  more  particularly  ; referring  to  Plate  XXIIL,  in  which  the  arrangement  of 
bricks  of  different  thickness  so  as  to  form  English  Bond  is  shown,  in  figs.  7,  9, 
12,  and  13. 


166 


PRACTICAL  MASONRY. 


The  bond  of  a wall  eight  inches  is  represented  by  fig.  7.  In  order  to  prevent 
two  upright  or  vertical  joints  from  running  over  each  other,  at  the  end  of  the  first 
stretcher  from  the  corner  place  the  return  stretcher,  which  is  a header,  in  the  face 
that  the  stretcher  is  in  below,  and  occupying  half  its  length ; a quarter  brick  is 
placed  on  its  side,  forming  together  six  inches,  and  leave  a lap  two  inches  for  the 
next  header,  which  lies  with  its  middle  upon  the  middle  of  the  header  below,  and 
forms  a continuation  of  the  bond.  The  three-quarter  brick,  or  brick-bat,  is  called 
a closer. 

Another  way  of  effecting  this  is  by  laying  a three-quarter  bat  at  the  corner  of 
the  stretching  course ; for,  when  the  corner  head  comes  to  be  laid  over  it,  a lap  of 
two  inches  will  be  left  at  the  end  of  the  stretchers  below  for  the  next  header ; 
which,  when  laid,  its  middle  will  come  over  the  joint  below  the  stretcher,  and  in 
this  manner  form  the  bond. 

/n  a twelve-inch,  or  brick-and-half  wall,  {fig.  9,)  the  stretching  course  upon 
one  side  is  so  laid,  that  the  middle  of  the  breadth  of  the  bricks  upon  the  opposite 
side  falls  alternately  upon  the  middle  of  the  stretchers  and  upon  the  points  be- 
tween the  stretchers. 

In  a two-brick  wall,  (fig.  12,)  every  alternate  header,  in  the  heading  course,  is 
only  half  a brick  thick  on  both  sides,  which  breaks  the  joints  in  the  core  of  the 
wall. 

In  a two-brick- and-a-half  wall,  (fig-  13,)  the  bricks  are  laid  as  shown  in  fig.  6. 

Flemish  bond,  for  an  eight-inch  wall,  is  represented  in  fig.  8,  wherein  two 
stretchers  lie  between  two  headers,  the  length  of  the  headers  and  the  breadth  of 
the  stretchers  extending  the  whole  thickness  of  the  wall. 

In  a brick-and-half  Flemish  bond,  (fig.  10,)  one  side  being  laid  as  in  fig.  2, 
and  the  opposite  side,  with  a half-header,  opposite  to  the  middle  of  the  stretcher, 
and  the  middle  of  the  stretcher  opposite  the  middle  of  the  end  of  the  header. 

Fig.  5 exhibits  another  arrangement  of  Flemish  bond,  wherein  the  bricks 
are  disposed  alike  on  both  sides  of  the  wall,  the  tails  of  the  headers  being  placed 
contiguous  to  each  other,  so  as  to  form  square  spaces  in  the  core  of  the  wall  for 
half-bricks. 

The  face  of  an  upright  wall,  English  bond,  is  represented  by  fig.  18,  and  that 
of  Flemish  bond  by  fig.  19. 


SECTION  VI.  — The  Construction  of  Chimneys. 

Many  able  and  scientific  men  have  treated  on  this  subject,  but  the  result  of 
their  observations  serves  only  to  prove,  what  is  the  result  of  every  day’s  experi- 


ON  THE  CONSTRUCTION  OF  CHIMNEYS. 


167 


ence,  namely,  that  rarefied  air  is  lighter  and  less  dense  than  cold  air ; and  that 
it  will  ascend  with  a velocity  proportionate  to  its  rarefaction,  unless  obstructed  by 
other  bodies. 

Heat,  that  is  generated  by  the  combustion  of  fuel,  exists  under  two  distinct 
forms ; and  is  known  by  the  names  of  combustible  and  radiant  heat.  Combus- 
tible heat  partakes  of  smoke,  and  is  carried  off  with  it  into  the  upper  regions  ; 
while  radiant  heat  is  communicated  to  opposing  bodies  in  contact  wdth  its  rays. 

It  is  stated  by  some,  that  combustible  heat  combined  with  air  and  smoke  exists 
in  the  proportion  of  four  to  one,  compared  to  radiant  heat ; but  its  correct  pro- 
portion has,  perhaps,  never  been  ascertained. 

It  is,  however,  certain,  that  very  little  radiant  heat  will  escape  from  a smothered 
combustion,  while  a dense  smoke  will  very  slowly  ascend,  and  sometimes  a por- 
tion of  it  is  discharged  into  the  room,  and  the  chimney  is  pronounced  smoky, 
while  the  epithets  uttered  against  masons,  on  such  occasions,  would  be  more 
properly  applied  to  the  builders  of  the  fire. 

As  nature  acts  by  certain  laws,  we  may  derive  more  profitable  information  by 
a proper  observance  of  them,  than  from  accidental  occurrences. 

It  is  one  of  the  laws  of  nature  that  rarefied  air  ascends,  while  cold  or  dense  air 
descends.  On  the  same  principle,  water  discharges  itself  most  copiously  through 
a channel  of  a uniform  and  direct  surface,  on  the  same  inclination.  Therefore, 
channels,  that  are  obstructed  by  eddies  and  the  discharge  of  other  streams  into 
them,  are  impeded,  and  the  velocity  of  the  water  diminished,  so  as  often  to  pro- 
duce what  is  called  back-water  for  a considerable  distance,  which,  when  removed, 
permits  the  water  to  flow  with  rapidity.  Short  bends  and  turnings  also  present 
obstacles  to  the  current  or  flow  of  water,  by  which  whirlpools  are  often  seen  in 
actual  contact  with  the  natural  stream.  The  same  observations  may  be  applied 
to  rarefied  air  or  smoke.  Hence  those  flues  will  carry  smoke  the  best  which 
arise  perpendicularly  in  a uniform  direction. 

Angles  and  turnings  present  obstacles  to  the  progress  of  the  smoke,  and  should 
be  avoided  as  much  as  possible. 

Particular  attention  should  be  paid  to  the  formation  of  the  throat  of  the  chim- 
ney. The  dimensions  of  which  should,  in  no  case,  exceed  the  number  of  square 
inches  contained  in  a horizontal  section  of  the  flue.  It  has  been  contended  by 
some  that  it  should  be  smaller  than  this,  while  others  have  thought  that  it  should 
be  larger;  but  experience  has  shown  both  of  these  opinions  to  be  erroneous. 
When  the  throat  is  smaller,  the  frequent  rushes  of  cold  air  into  it,  from  the  open- 
ing of  doors,  &.C.,  sends  a gush  of  smoke  into  the  room,  by  obstructing  the  up- 
ward current  of  rarefied  air. 

When  the  throats  are  larger,  eddies  are  formed  in  them,  and  the  smoke,  be- 


168 


PRACTICAL  MASONRY. 


coming  dense  by  the  steam  of  the  fuel,  chokes  the  flue,  and  instead  of  ascending 
is  puffed  into  the  room. 

Experience  has  shown  the  best  construction  to  be  that  where  the  throat  con- 
tains as  many  square  inches  as  a section  of  the  flue.  If  the  latter,  for  instance? 
is  one  hundred  and  forty-four  inches,  the  throat  should  be  four  feet  long,  and 
three  inches  wide,  nearly  on  a level  with  the  mantel-bar,  or  at  the  top  of  the 
opening  of  the  fire-place,  and  graduated  to  the  regular  dimensions  of  the  flue. 

As  represented  in  Plate  XXVII.,  3 and  4.  In  this  plate,  fig.  3 shows  a 
side  perpendicular  section  of  a chimney  ; d,  the  partition -wall ; a,  the  throat ; b, 
the  breast ; c,  the  height  of  the  graduation  to  form  the  regular  flue ; E,  the  depth 
of  the  jamb  ; /,  a trimmer  to  support  the  hearth  in  form  of  a segment  arch. 

Fig.  4 is  the  front  elevation  of  fig.  3,  representing  the  flues,  fire-places,  a hori- 
zontal section  at  the  heai'ths,  as  D E ; a section  of  the  flues  at  the  side  of  the  fire- 
places, I ; the  core  of  the  chimney,  H ; the  jambs,  F ; the  back  of  the  fire- 
places, G,  with  the  inclined  part  of  the  back. 


SECTION  VII.-Fibe-Places. 

In  the  selection  of  materials  for  the  construction  of  fire-places,  those  should  be 
preferred  which  contain  the  least  metallic  ingredients.  Metals  are  absorbents  of 
heat,  and  consequently  occasion  less  heat  to  be  radiated  into  the  room,  than  ma- 
terials of  a different  nature.  Soapstone  has  been  found  to  be  one  of  the  best 
materials  for  this  purpose.  It  contains  but  little  metallic  substance  compared  to 
brick  ; it  is  capable  of  a high  degree  of  polish,  and  of  being  easily  kept  clean,  by 
which  means  the  mys  of  heat  are  reflected  into  the  room. 

The  proportions  of  a fire-place  should  in  some  degree  be  regulated  according 
to  the  size  of  the  room  which  it  is  intended  to  warm. 

If  the  room  is  eighteen  feet  in  length,  a fire-place  of  four  feet  three  inches  in 
width,  from  jamb  to  jamb,  and  three  feet  in  height,  where  the  room  is  tw'elve  feet 
in  the  same  direction,  or  one  fourth  of  the  height  of  the  room,  may,  in  general, 
be  considered  of  suitable  proportions.  The  jambs  should  form  an  angle  of  one 
hundred  and  thirty-five  degrees  with  the  back.  See  Plate  XXVII.,  fig.  4.  H, 
the  jamb,  the  back  edge  of  which  should  be  rabbeted  and  fitted  to  a groove 
in  the  back,  to  keep  it  in  its  place ; F should  be  set  plumb  about  two  fifths  of  the 
height  of  the  back,  F G ; G should  be  inclined  forward  to  within  seven  inches  of 
the  front  line,  allowing  four  inches  for  the  thickness  of  the  breast,  and  three  inch- 
es will  remain  for  the  passage  of  the  smoke. 

The  Communication  of  Hot  Air  to  Rooms.  — This  subject  is  worthy  of  attention. 


I , ‘I* 


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OF  FIRE-PLACES. 


169 


inasmuch  as  the  temperature  of  bed-chambers  may  be  regulated  by  it  as  well 
as  the  danger  of  fire,  and  the  destructive  and  fatal  effects  of  charcoal  diminished. 
This  improvement  may  be  adapted  to  common  fire-places  as  well  as  to  grates, 
and  the  hot  air  carried  from  the  first  to  the  upper  stories. 

A little  below  the  hearth  in  the  first  story,  a small  aperture  is  opened,  of  about 
two  inches  square,  through  which  to  receive  fresh  air  from  the  outside  of  the 
house,  into  a cavity  as  large  as  can  with  convenience  be  made  between  the  jambs 
and  the  brick  which  form  the  wall  of  the  chimney ; this  cavity  should  be  made 
tight,  with  an  aperture  for  the  insertion  of  tubes  of  copper  or  tin,  which  are  to  be 
inserted  in  the  aperture  with  stops  or  slides,  to  regulate  the  quantity  of  air  to 
be  admitted  into  the  room.  The  air  enters  about  two  feet  from  the  floor.  By 
turning  the  slide,  the  air  is  made  to  ascend  into  other  apartments  at  pleasure. 

Plate  XXVII,,  fig.  4,  L is  the  generator  of  rarefied  air;  o,  the  tube,  with  a 
slide  at  k ; the  ascending  pipe  should  be  about  four  inches  square  ; m shows 
its  passage  at  the  hearth. 

Chimney-pieces  are  of  various  forms,  as  the  fancy  or  taste  of  the  proprietor 
may  dictate. 

In  Plate  XX^'III.,  /ty.  1 is  a Doric  chimney-piece.  Xo.  1,  a section  of  the 
jambs,  back-facing,  plinth,  and  pillars,  drawn  on  a scale  of  lialf  an  inch  to  a 
foot;  Xo.  2,  the  shelf.  Fig.  2 represents  an  Ionic  chimney-piece;  Xo.  1,  a sec- 
tion ; Xo.  2,  the  shelf;  the  line  a shows  a projection  of  the  entablature;  b,  the 
facins:  under  the  entablature,  drawn  on  a scale  of  half  an  inch  to  a foot. 


SECTION  VIII.  — Warming  by  Steam  and  Hot  Water. 

Perkins's  Patent  is  upon  a principle  that  will  bear  investigation.  The  cooking- 
range  is  made  with  a hollow  cast-iron  back,  to  hold  from  four  to  five  gallons,  with 
copper  pipes,  introduced  one  at  the  bottom  and  one  at  the  top  ol  this  back,  ex- 
tending near  three  teet  from  the  boiler,  of  one  and  a half  to  two  inches  calibie ; 
then  lead  pipe  of  the  same  size  to  be  carried  to  the  rooms  to  be  warmed  ; there 
lay  a coil  of  about  forty  feet  of  pipe  ; the  coil  may  be  inclosed  in  a chamber  to 
imitate  a piece  of  furniture,  thence  carried  to  all  the  apartments  in  the  house, 
and  returned  to  the  under  pipe  connected  with  the  hollow  back,  having  the  whole 
tightly  closed  by  soldering;  then  introduce  an  aperture  at  the  highest  point 
made  convenient  for  filling  with  water.  When  filled,  close  the  aperture,  when,  by 
the  common  use  of  the  range,  a current  is  produced  in  the  water  within  the  pipe^ 
passing  from  the  upper  pipe  heated,  and  returning  through  the  lower  pipe  to  re- 
new the  revolution.  There  being  no  escape  for  steam,  one  filling  will  last  a con- 

22 


170 


PRACTICAL  MASONRY. 


siclerable  time  without  renewing  the  water.  Another,  and,  as  we  think,  a still 
better,  method  of  warming  houses,  or  other  buildings,  by  means  of  heated  water, 
is  that  of  Mr.  Dexter,  of  this  city.  The  following  is  a description  of  this  meth- 
od, as  exemplified  in  the  house  of  Mr.  S.  K.  Williams,  No.  68  Boylston  Street. 
A chamber  of  brick-work  is  built  in  the  cellar,  under  the  front  entry,  containing 
three  hundred  and  sixty  cubic  feet ; under,  and  near  the  centre,  is  a grate  simi- 
lar to  those  used  for  Bryent  and  Herman’s  furnaces,  over  which  is  set  a copper 
boiler,  holding  thirty-two  gallons.  On  one  side  of  the  boiler  are  fifty-four  copper 
tubes,  four  inches  in  diameter,  and  four  feet  long,  set  perpendicular,  and  resting 
upon  a table  of  brick -work,  three  and  a half  feet  above  the  bottom  of  the  cellar, 
connected  by  six  semi-cylindrical  pipes,  five  feet  in  length,  entering  from  the  boil- 
er, and  parallel  to  each  other,  and  uniting  with  the  boiler  at  the  bottom.  The 
upper  ends  of  the  tubes  are  united  with  each  other  in  a transverse  direction  ; 
also,  in  a semicircular  form,  a tube  connecting  with  the  boiler,  near  the  top, 
of  the  same  size.  The  boiler  is  a cylinder,  set  upright  above  the  brick-work, 
four  feet  in  height,  and  extends  nearly  to  the  height  of  the  tubes.  In  the 
entry,  above,  is  set  a copper  vessel,  with  a lid  to  shut  tight,  containing  sixteen 
gallons  ; a tube  three  fourths  of  an  inch  in  diameter  enters  near  the  bottom, 
passing  down  through  the  air-chamber  into  the  boiler,  for  the  purpose  of  filling  by 
a force-pump  ; a stop-cock  is  inserted  in  the  vessel  at  the  top,  to  supply  the  boil- 
er with  cold  water.  The  heated  water  is  drawn  from  the  same  boiler  for  warm 
baths,  and  from  this  air-chamber  are  funnels,  registers,  and  dampers,  entering 
parlours,  entry,  <Scc.  To  communicate  direct  heat  to  the  chambers,  there  is  a 
wooden  box,  ten  by  fourteen  inches  square,  set  perpendicular  against  the  wall  of 
the  entry,  passing  up  to  the  entry  above,  or  communicating  with  the  rooms  by 
horizontal  pipes  and  registers  through  the  floor.  At  one  side  of  the  grate  is  a 
projection  of  brick-work,  inclosing  a metallic  cylinder,  fourteen  or  fifteen  inches 
in  diameter,  and  about  four  and  one  half  feet  perpendicular,  the  top  of  which 
communicates  with  a register  by  a horizontal  pipe.  Near  the  bottom  of  this 
cylinder  is  a horizontal  branch,  to  admit  the  heated  air  from  the  large  chamber  to 
the  small  one.  The  smoke-pipe  passes  from  the  grate  into  the  large  chamber, 
entering  the  perpendicular  cylinder  through  the  lower  branch,  thence,  through 
one  side  of  the  cylinder,  horizontally  to  the  chimney  flue  ; thus  leaving  sufficient 
space  to  admit  the  heat  from  the  large  chamber  into  the  cylinder,  around  the 
smoke-pipe.  To  admit  cold  air  into  the  chamber  a flue  is  provided  twelve 
inches  in  diameter  to  enter  in  a downward  direction  under  the  front  door-steps. 
This  flue  passes  horizontally  under  the  cellar  floor,  rises  in  a perpendicular  direc- 
tion, and  enters  the  chamber  near  the  top.  The  cold  air  finds  its  way  through  the 
hot  air  in  the  chamber,  and  becomes  sooner  rarefied  than  when  entering  near  the 


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OF  FURNACES. 


171 


bottom  of  the  chamber.  This  experiment  by  Mr.  Dexter  is  highly  successful.  It 
is  secure  against  any  eruption  from  the  boiler  or  pipes,  to  the  injury  of  the  house 
or  its  occupants.  The  rarefied  air,  thus  obtained,  produces  a sensation  similar  to 
that  produced  by  sitting  in  a room  with  the  windows  up  in  June.  In  effect, 
winter  is  thus  changed  into  summer. 

Dexter’’ s Apparatus  for  icarming  Dwelling-houses,  ^'c.  — Plate  XXIX.,  fg.  1, 
a,  the  cylinder  for  heating  water ; b,  b,  &c.,  perpendicular  tubes ; c,  lower  pipe, 
connecting  with  the  boiler  ; d,  upper  pipe,  connected  with  the  boiler  at  the  top  ; 
e,  small  chamber,  heated  by  the  smoke-pipe,  also  from  the  hot-air  chambers ; f, 
smoke-pipe  ; g,  g,  brick  table  containing  the  grates  and  supporting  the  apparatus  ; 
h,  fire-grates ; i,  ceiling  or  floor  above  the  air-chamber ; j,  ash-pit ; k,  cold-air 
flue  ; I,  brick  floor. 

Fig.  2,  horizontal  section  or  plan  ; a,  boiler  ; b,  small  chamber  ; e,  smoke-flue  ; 
g,  brick  table ; h,  cold-air  flue ; i,  i,  &.C.,  semicircular  pipes  ; m,  m,  &c.,  walls  of 
the  hot-air  chamber. 

Blaneifs  J Voter  Furnace,  for  warming  the  air  in  dwelling-houses  through  the 
medium  of  hot  water.  The  air  is  conducted  from  an  air-chamber,  through  pipes 
and  registers,  to  the  several  apartments.  The  chamber  is  made  of  brick,  con- 
taining about  five  hundred  cubic  feet,  in  which  the  apparatus  is  placed.  The 
apparatus  (see  No.  1,  Plate  XXX.,  fig.  1)  consists  of  an  upright  cast-iron  cylindric 
boiler,  about  two  feet  in  diameter  ; b,  steam-condenser  ; G,  G,  G,  &,c.,  cast-iron 
pipes ; d,  the  door  for  fuel ; c,  the  ash-pit  in  a square  base,  on  which  the  cylin- 
der stands.  No.  2,  a vertical  section  ; h,  is  the  grate  for  coal ; i,  the  boiler  to  be 
filled  with  water ; g,  smoke-funnel ; the  darts  show  the  dhection  of  the  draft  and 
smoke  ; k,  the  ash-pit. 

Fig.  2,  a horizontal  section  ; h,  the  grate  ; i,  the  cavity  filled  with  water,  sur- 
rounding the  grate  and  fire-place,  smoke-flue,  door-way,  &c. ; g,  the  smoke-fun- 
nel ; G,  G,  G,  &.C.,  cast-iron  pipes ; k,  cold-air  conductor ; /,  I,  walls  of  the  air- 
chamber. 

Operation.  — The  boiler  and  pipes  are  filled  with  water,  also  the  steam-con- 
denser about  two  thirds,  leaving  six  inches  of  the  upper  part  of  the  condenser 
for  steam  ; when  the  water  is  at  a boiling  heat,  it  flows  from  the  boiler  and  falls 
into  the  condenser,  and  descends  through  the  pipes  to  the  bottom  of  the  boiler, 
and  renews  the  heat  from  the  fire  and  passes  on  as  before,  through  the  conden- 
ser, &c. ; the  revolution  of  the  water  will  be  in  proportion  to  the  degree  of  heat 
to  which  it  is  raised.  The  fresh  air  is  admitted  through  the  conductor,  from  the 
outside  of  the  building,  to  the  hot-air  chamber,  and  is  heated  as  it  comes  in  contact 
with  the  boiler,  tubes,  &lc.,  and,  passing  through  tin  or  sheet-iron  funnels,  is 
admitted  into  the  apartments  through  a register  in  the  floor. 


172 


' PRACTICAL  MASONRY. 


Blaneifs  Furnace.  — This  portable  furnace  is  much  in  use,  and  gives  general 
satisfaction  for  dry  heat ; it  is  used  in  dwelling-houses  and  public  buildings  with 
success. 

Plate  XXXIIL,  1,  elevation ; fig.  2,  vertical  section ; the  external  air  passes 
from  the  air-drain  A,  to  the  air-box  B,  through  the  tube  C,  into  the  cold-air 
chamber  D,  whence  it  rushes  into  the  hot-air  chamber  E,  through  the  apertures 
F,  F,  acting  with  rapidity  upon  the  heated  cylinder  H,  and  the  inner  surface  of  the 
rarefying  tubes  I,  I,  and  ascends,  through  the  register  M,  into  the  apartment  to 
be  warmed. 

A,  air-drain;  B,  air-box;  C,  tubes  to  connect  the  air-box  with  the  cold-air 
chamber ; D,  cold-air  chamber ; E,  hot-air  chamber  ; F,  apertures  ; G,  reflecting- 
case ; H,  fuel-cylinder  ; I,  I,  rarefying  tubes ; K,  ash-pit ; L,  smoke-pipe ; M, 
register;  N,  branch  from  the  hot-air  chamber;  O,  O,  dampers.  Fig.  3,  plan  of 
the  base,  C,  C,  Slc.,  to  connect  the  air-box  with  the  cold-air  chamber.  Fig.  4, 
register. 

Plate  XXXI.  shows  the  method  of  constructing  kitchen  fire-places,  for  heating 
boilers,  stew-pans,  and  other  culinary  apparatus.  Fig.  1,  a vertical  section,  as  rep- 
resented on  the  plan,  jig.  2,  by  the  dotted  line  aa ; Jig.  2,  plan  for  a double  boiler, 
one  set  over  the  grate,  the  other  over  the  space  B ; C,  the  con.struction  of  the  flue, 
which  is  to  be  regulated  by  a slide  (/,  d,  d,  the  slope  of  brick-work  rising  above 
the  sides  of  the  grate.  In  this  construction,  one  boiler  is  fixed  immediately  over 
the  grate,  and  the  other  is  placed  over  the  space  shown  at  h ; the  space  b is  made 
sufficiently  capacious  to  admit  a large  proportion  of  the  heated  current  of  air,  the- 
direction  of  which  is  shown  by  darts,  the  flue  being  so  constructed  as  to  com- 
pletely envelope  the  external  surface  of  the  two  boilers.  If  the  Hues  were  made 
all  the  way  along  their  course  of  equal  capacity  with  the  space  contained  around  the 
grate,  it  is  very  clear,  that,  when  the  air  became  rarefied  by  the  combustion  of  fuel, 
it  would  move  in  every  part  with  an  equal  velocit}^  and  the  greatest  portion  of  the 
heat  would  escape,  without  being  imparted  to  the  vessel  and  its  contents  intend- 
ed to  be  heated.  In  order  to  prevent  this,  the  area  of  the  flue  is  contracted  at  c, 
by  which  means  the  heated  air  is  detained  much  longer  under  the  bottom  of  the 
boiler,  and,  impinging  upon  the  surface  of  the  vessel,  tends  to  heat  in  the  most  ad- 
vantageous manner,  it  being  a well  known  fact  that  heat  is  best  communicated  by 
ascent ; therefore,  it  will,  at  all  times,  be  advantageous  to  detain  the  heated  current 
as  long  as  possible  while  it  is  covered  by  the  under  surface  of  the  boiler.  These 
reasons,  if  duly  attended  to,  will,  in  every  case,  suggest  to  the  practical  bricklayer 
the  most  advantasreous  situation  to  construct  the  cheak  or  diminished  area  for  the 
passage  of  the  heated  currrent.  In  cases  where  very  great  economy  is  requisite, 
as  in  steam-engine  boilers,  &.C.,  the  advantage  of  the  ascending  property  of  heat 


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OF  FURNACES. 


173 


is  so  well  understood  by  engineers,  that  they  make  the  sides  of  their  boilers  pro- 
ject so  as  to  form  the  upper  surface  of  the  enveloping  flue,  by  which  means  they 
not  only  avail  themselves  of  the  lateral  heat  of  the  current,  but  also  of  that  most 
important  property  before  stated,  namely,  the  ascending. 

The  sides  around  the  grate,  shown  at  d,  d,  d,  d,  d,  should  rise  in  a sloping 
direction,  so  as  to  accommodate  the  space  to  the  rarefied  air,  after  it  has  been 
heated  by  the  combustion  of  fuel;  and  as  these  sides  will  have  to  sustain  the 
greatest  action  of  the  heat,  they  being  many  times  covered  with  the  ignited  fuel, 
it  is  absolutely  requisite  that  they  should  be  formed  of  the  best  fire-bricks  and  set 
in  Stoarbridge  clay,  or  fire-loam,  mixed  with  ground  clinkers  from  smiths’  forges, 
which,  when  heated,  will  form  a semi-vitrified  mass  that  will  bind  and  unite  the 
whole  mass  firmly  together.  In  all  cases  where  it  can  be  admitted,  the  approach 
to  the  narrowed  passage  to  the  current  should  be  made  to  slope  gradually  up- 
wards, which  will  assist  to  contract  the  current,  like  a funnel,  at  the  same  time  that 
such  an  effect  is  greatly  assisted  by  changing  the  direction  of  the  heated  medium. 

In  the  construction  of  fire-places,  in  which  it  is  intended  that  the  heated  air 
should  be  made  to  strike  or  impinge  against  any  vessel  in  order  to  raise  the  tem- 
perature of  its  contents,  it  will  be  of  the  greatest  importance  to  have  all  the  brick- 
work done  in  the  most  thorough  manner  possible,  as  nothing  can  be  more  injuri- 
ous than  cracks  or  openings,  which,  by  being  connected  with  the  flues,  admit 
cold  air  into  the  heated  current,  and  thereby  destroy,  in  a great  measure,  the 
effect  intended.  To  the  practical  man,  who  is  aiming  at  eminence  in  his  profes- 
sion, we  cannot  too  much  enforce  these  observations,  as  they  have  been  practical- 
ly proved  to  be  of  the  greatest  importance. 

Before  concluding  these  observations  upon  the  construction  of  this  class  of  fire- 
places, we  wish  most  strenuously  to  impress  upon  our  practical  readers  the  mis- 
taken and  false  economy  of  making  fire-grates  too  small,  a practice  that  most 
completely  defeats  the  principal  object  in  view,  namely,  that  of  saving  fuel. 
A very  little  reflection  will  clearly  show,  that  where  the  space  for  fuel  is  too 
small,  the  want  of  room  to  spread  the  fuel  will  cause  it  to  lay  in  such  a compact 
and  solid  state,  that  the  gaseous  parts  will  be  distilled  and  pass  along  the  flue 
without  being  ignited,  and  by  such  means,  instead  of  imparting  heat  by  entering 
into  combustion,  a precisely  contrary  effect  will  be  produced.  And  if,  on  the 
other  hand,  very  small  portions  of  fuel  are  frequently  supplied,  the  opening  of  the 
door  of  the  fire-place  so  repeatedly  will  permit  so  much  cold  air  to  enter  as  to 
essentially  diminish  the  heating  of  the  vessel  and  its  contents,  independently  of 
the  great  loss  of  time  that  will  be  required  to  keep  up  a steady  heat. 

There  is  also  another  circumstance  of  great  importance,  which  must  be  admit- 
ted into  the  consideration  of  this  subject,  namely,  that  where  fire-places  are  made 


174 


PRACTICAL  MASONRY. 


sufficiently  large,  fuel  of  a much  coarser  description  can  be  used,  and  a very 
equable  and  economical  heat  may  be  produced  ; for,  in  such  cases,  the  cinders 
and  ashes  from  the  common  fire-grates,  when  mixed  with  a due  proportion  of 
small  coals,  will  be  not  only  sufficient  for  creating  a proper  heat,  but  will  not 
require  half  the  attendance  that  pure  coals  with  a pinched  fire-place  will  do. 

We  have  been  induced  to  make  these  observations,  from  a perfect  convic- 
tion of  their  practical  utility,  having  frequently  observed  the  great  loss  that 
accrues,  and  the  serious  inconvenience  that  is  sustained  by  many  families  who 
have  employed  persons  to  set  the  ordinary  kitchen  copper,  which  is  too  frequent- 
ly executed  upon  such  bad  principles,  that  a great  portion  of  the  advantages 
and  convenience  of  that  very  useful  apparatus  is  lost.  The  length  of  the  bars, 
in  most  cases,  should  be  about  three  fourths  of  the  diameter  of  the  bottom  of 
the  boiler,  and  if  they  are  loose  bars  they  will  be  much  better  than  a frame  cut 
with  all  the  bars  entire.  The  space  between  each  bar  should  be  about  half  an  inch. 
And  it  should  be  remembered  that  the  flues  of  this  kind  of  fire-places  are  as  likely 
as  others  to  be  clogged  with  soot,  and  therefore  it  will  be  very  requisite  to  have 
loose  bricks,  or  stoppers,  placed  in  proper  situations,  as  shown  at  c,fig.  2,  which 
will  give  great  facility  in  cleansing  such  flues,  and  frequently  prevent  danger  from 
fire  in  buildings  where  they  may  be  erected.  It  may  be  necessary  to  state,  that 
the  same  precautions  and  directions  ought  to  be  observed  in  figs.  3,  4,  and  5,  as 
in  figs.  1 and  2.  Figs.  3 and  4 represent  a section  and  plan  of  a hot  plate,  fig.  3, 
which  is  most  generally  of  cast-iron,  resting  about  an  inch  on  the  brick-work  all 
round,  and  a rim  of  wrought-iron  should  be  fixed  round  the  external  brick-work, 
to  protect  it  from  being  broken  or  otherwise  damaged.  The  bridge  of  fire-brick 
ought  to  be  built  to  within  three-quarters  of  an  inch  of  the  plate,  leaving  that 
distance  between  the  bridge  and  the  under  part  of  the  plate  for  the  smoke  and 
heat  to  pass  on  the  way  to  the  chimney.  The  dotted  line,  in  fig.  3,  shows  the 
position  of  the  flue  and  the  chimney.  Fig.  5 is  the  plan  of  the  copper  boiler,  with 
the  bottom  part  contracted  round  the  grate.  The  same  rises  at  the  opening  in 
the  back,  passes  round  the  bottom,  and  then  enters  the  chimney. 

Fig.  5 is  the  representation  of  a charcoal -stove,  which  is  composed  of  solid 
brick- work,  except  it  should  so  happen  that  a veiy  large  one  should  be  wanted ; 
then  the  wall  may  be  built  hollow  and  filled  up  with  rubble.  The  grates  are  con- 
structed of  cast-iron,  and  placed  four  inches  deep,  with  a vacuity  under  the  floor 
for  the  ashes  to  drop,  whence  they  may  be  drawn  out  through  the  cavity  left 
in  the  front.  Stoves  of  this  description  are  used  for  stew-pans,  chafing-dishes,  &lc. 
A rim  of  wrought-iron  should  be  fixed  round  the  brick-work  at  the  top,  about  three 
and  a half  inches  deep,  or  a covering  of  soap-stone  an  inch  and  a half  thick, 
properly  fitted ; the  grates  are  of  different  sizes,  according  to  the  magnitude  of 
the  building. 


W.WM'ns/w  h'r. 


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OF  FURNACES. 


175 


On  the  Method  of  fixing  a Copper  Boiler  for  Brewing.  — Fig.  1,  Plate  XXXII., 
is  a section  through  the  upper  vertical  line  in  the  middle  of  the  copper ; fg.  2 is  a 
horizontal  section  of  the  copper  taken  under  the  bottom,  and  may  be  considered 
as  the  plan  of  the  brick- work  immediately  above  the  grate.  This  method  offers 
the  least  obstruction  for  the  flame  to  play  on  both  sides  where  it  meets  on  the  op- 
posite side  of  the  prop  at  A,  and  thence  rises  in  a sloping  direction  towards  the 
back,  which  is  shown  by  another  section,  fg.  3,  the  part  at  A being  the  partition, 
as  shown  on  the  plan,  fg.  2.  Above  the  partition,  A,  the  whole  of  the  smoke 
rushes  into  a chimney  or  tube  ascending  up  the  back  of  the  brick-work,  and  is 
discharged  into  the  atmosphere  at  the  top.  This  chimney  is  shown  in  the  sec- 
tion, fg.  3,  which  is  taken  at  right  angles  to  fig.  2,  as  exhibited  by  the  plan, 
fg.  4,  which  is  the  plan  of  the  second,  fig.  3.  Fig.  6 is  an  elevation  of  the  front, 
showing  the  fire-place  and  the  manner  of  suspending  the  door  by  means  of 
pulleys,  which  is  balanced  by  a weight  depending  from  the  remote  pulley ; the 
top  of  the  brick  casing  round  the  copper  is  entirely  closed  round  the  circumfer- 
ence, as  shown  on  the  three  sections  at  a a,  a a,  &cc.  There  is  a similar  ring  of 
brick-work  which  encompasses  the  circumference  of  the  copper,  and  is  also 
shown  on  these  sections,  nX  bb,  b b,  <Scc.  This  construction  is  that  recommended 
by  i\Ir.  David  Booth,  a gentleman  well  known  by  his  numerous  publications,  and 
his  scientific  acquirements  on  practical  and  useful  subjects.  We  cannot  conclude 
this  department  of  instruction  without  again  enforcing  upon  our  scientific  friends 
the  absolute  necessity  of  making  the  atmospheric  air  fall  tlirough  the  ignited 
fuel,  and  also  of  taking  especial  care  that  their  work  may  be  made  so  close  and 
sound  as  to  prevent  a circulation  of  that  which  is  very  properly  called  the  pabu- 
lum of  life  and  flame  ; for  one  fact  should  never  be  lost  sight  of  for  an  instant, 
namely,  that  whatever  air  is  admitted,  without  being  decomposed  or  used  up  by 
the  fuel,  must  of  course  tend  to  impart  its  own  temperature  to  the  surrounding 
objects,  and  consequently  rather  retard  than  accelerate  the  object  in  view.  We 
are  well  aware,  that,  however  well  fire-places  of-this  kind  may  be  constructed,  much 
evil  is  frequentl}'  produced  by  having  to  join  the  flue,  or  carry  it  into  one  already 
formed.  In  such  case  it  will  generally  be  well  to  continue  the  flue  belonging  lO 
the  boiler  fire-place  to  as  great  an  extent  as  possible,  before  it  enters  the  flue 
already  formed,  which  will  assist,  in  some  degree,  to  obviate  the  difficulty.  A 
portion  of  the  flue  that  leads  from  the  one  not  in  use  should  be  stopped,  to  pre- 
vent the  entrance  of  air  through  it  at  such  part. 

Bryent  and  Herman.' s Furnace.  — In  building  the  brick-work  for  the  furnace 
with  an  oven,  the  outside  wall  should  be  four  feet  six  inches  wide,  by  four  feet 
deep  from  front  to  rear,  as  seen  in  Plate  XXXW .,  fg.  3. 

Hot-air  Furnace  with  Oven.  — Lay  your  foundation  four  feet  six  inches  wide 


176 


PRACTICAL  MASONRY. 


by  four  feet  deep,  and  you  will  require  as  much  as  seven  feet  four  inches  in  height. 
In  laying  out  the  foundation,  you  will  build  an  eight-inch  wall  to  place  the  plate 
on  that  supports  the  pot  marked  C ; this  wall  makes  your  ash-pit ; carry  this 
wall  up  as  high  as  the  top  of  the  door  marked  i ; you  will  have  two  other  walls, 
C and  K,  four  inches  thick,  being  four  inches  apart;  carry  these  walls  nearly  as 
high  as  the  plate,  then  head  over  the  open  spaces,  so  that  the  whole  work  shall  be 
flush  with  the  top  of  the  plate.  You  will  set  bricks  on. end  for  the  inner  course, 
far  enough  apart  to  allow  the  lengths  of  bricks  to  span  from  centre  to  centre  in 
laying  flatways ; this  will  leave  holes  about  five  and  a half  inches  wide  and  seven 
and  a half  inches  high  ; you  will  then  proceed  with  this  wall  solid,  four  inches 
thick,  as  below,  up  to  the  top  of  the  oven,  when  the  hot-air  pipe  B,  that  goes 
under  the  covering  can  be  put  in ; also  the  smoke-pipe  C ; you  will  then  fill  round 
the  pipes  even  with  the  top  of  the  pipes  and  cover  over  with  bottom-stone,  or  iron 
bars  and  bricks.  Now  your  inner  wall  is  completed,  your  outside  wall  will  con- 
tinue as  begun  till  you  get  about  seven  or  eight  inches  above  the  inner  cover- 
ing, when  that  may  be  covered  as  the  other,  leaving  a space  open  on  one  side 
for  the  cold  air  to  enter,  recollecting  to  set  the  bottom  of  the  water-door  even  with 
the  plate,  and  of  course  leaving  a hole  through  both  walls  the  size  of  the  water- 
door.  Care  should  always  be  taken  that  the  brick  and  mortar  do  not  touch  the 
mouth  or  feeding  door  on  the  sides  or  top ; if  it  does,  the  expansion  of  the  iron, 
when  heated,  will  crack  the  brick.  The  smoke-pipe  should  always  be  kept  two 
and  a half  to  three  inches  below  the  lower  covering  stone,  to  allow  of  its  being 
taken  out  to  repair  if  necessary  without  removing  the  covering  stones.  In  setting 
the  furnace  with  a drum,  fig.  4,  the  work  is  nearly  the  same,  with  the  exception 
that  the  outside  of  the  brick-work  will  be  five  feet  wide  by  four  feet  six  inches  deep, 
receding  eight  inches  in  front,  having  the  recess  about  two  feet  wide.  Seven  feet 
high  will  answer  for  the  No.  2 furnace,  with  drum.  The  plans  given  here  are  for 
the  No.  2 furnace,  which  is  the  smallest  but  one.  There  are  three  sizes  larger, 
Nos.  2J,  3,  and  4.  The  size  of  the  brick-work  should  increase  six  inches  to  the 
size  No.  2},  five  and  a half  feet  by  five  feet ; No  3,  six  feet  by'  five  and  a half 
feet ; No.  4,  six  and  a half  feet  by  six  feet ; or  a little  less  than  the  above  will 
answer.  It  will  take  about  fourteen  hundred  brick  for  the  No.  2 furnace,  with  an 
oven,  and  about  sixteen  hundred  with  a drum. 

Fig.  1 represents  the  front  elevation  ; Fig.  2,  section  of  the  base  ; a represents 
the  cold-air  box  ; h,  hot-air  pipes ; c,  outside  of  the  elbow-tube ; d,  oven  ; e, 
smoke-pipe  ; /,  feeding  door  for  furnace ; g,  pot  that  contains  the  coal ; li,  pendu- 
lum grate  ; i,  ash  door  or  double  door  ; y,  inside  wall ; k,  sifter  grates  for  ashes  ; /, 
the  outer  wall ; m,  figs.  2 and  3,  hot-air  chamber ; n,  water-door ; o,  hole  in  the 
pendulum  grate  ; p,fig.  4,  drum  ; q,  collar  or  drum  to  receive  the  smoke-pipe  ; s, 
cold-air  passage. 


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CONSTRUCTION  OF  OVENS. 


177 


Stimpson^s  Patent  Radiating  and  Hot-air  Ranges.  — These  ranges  can  be 
set  either  with  or  without  the  bath-boiler.  They  can  also  be  set  with  hot-air 
fixtures,  to  heat  an  additional  room  with  the  same  fire.  They  are  manufactured 
of  various  sizes,  to  accommodate  families,  victualling  establishments,  boarding- 
houses, and  taverns.  They  were  originally  invented  more  than  fifteen  years 
since.  Many  thousands  have  been  sold,  and  have  been  in  use  from  ten  to  fifteen 
years.  They  have  been  lately  very  much  improved  and  newly  patented,  and 
are  believed  to  be,  so  far  as  economy  of  fuel,  convenience  of  arrangement,  dura- 
bility, and  facility  for  being  repaired,  are  good  qualities,  the  best  ranges 
now  in  use. 

Plate  XXXV.  Fig.  1 is  a front  elevation  of  the  range  with  bath -boiler  ; fig.  2, 
a horizontal  section  just  below  the  boiler  plates,  showing  the  course  of  the  flues  ; 
fig.  3 is  a vertical  section  of  the  boiler  and  Hues  connected  with  it ; fig.  4 is 
a vertical  section  through  the  middle  of  the  oven  and  of  the  fire-place,  showing 
the  course  of  the  oven -Hue. 

In  setting  the  range,  first  place  the  two  sides,  a,  a,  with  the  mantel,  b,  and 
the  grate,  c,  supporting  the  ends  of  the  side  grates  with  short  pieces  of  wood, 
till  the  brick  is  built  up.  Have  these  level  and  true,  and  be  careful  to  leave  space 
enough  between  them  to  allow  for  the  expansion  of  the  plate  which  goes  over  the 
fire.  Now  build  up  the  brick-work  level  with  the  top  of  these  sides,  leaving  the 
Hues,  as  indicated  by  dddd.  The  brick  back,  which  is  usually  set  with  them, 
forms  the  back  of  the  fire-place,  and  is  bevelled  at  the  top  to  fit  the  iron-work. 
Two  fire-bricks  (headers)  should  be  placed  undereach  of  the  side  boiler  holes,  and 
the  rest  of  the  space  under  the  boiler  holes  filled  with  common  brick,  taking  care 
to  leave  a space  of  one  inch  underneath  when  the  boilers  are  in.  Now  place  the 
oven  frame,  e,  and  the  oven  partition, y/;  also  the  boiler  casing,  g ; the  bottom  of 
this  casing  should  be  level  with  the  top  of  the  sides,  a,  a.  Build  up  around  the 
oven  with  face  brick.  The  space  for  the  Hues  at  the  side  is  shown  by  ledges  on 
the  cast-iron  partition,  f f ; the  space  back  of  the  oven  should  be  an  inch  and  a 
quarter.  Fill  in  around  the  boiler  casing  all  solid,  leaving  a Hue  at  the  top, 
which  should  enter  the  main  Hue. 


SECTION  IX.  — O.v  THE  Construction  of  Ovens,  Boilers,  Fire-places,  and  of  the 

Setting  of  Copper. 

The  section  of  the  roof  of  the  oven,  on  the  old  principle,  for  the  use  of  bakers 
is  usually  of  an  oval  figure,  being  arched  over  at  the  top  in  the  figure  of  an 
ellipsoid  ; the  sides  and  bottom  are  of  brick,  tiles,  and  lime,  with  a door  in  front ; 

23 


178 


PRACTICAL  MASONRY. 


and  at  the  upper  part  is  an  inclosed  closet,  with  an  iron  grating  for  the  tins  to 
stand  on,  called  the  proving-oven.  To  heat  such  ovens,  fagots  are  introduced 
and  burnt  to  ashes,  which  are  then  removed,  and  the  bottom  cleaned  out.  This 
operation  requires  some  time,  during  which  much  of  the  heat  escapes.  A still 
further  length  of  time  is  required  for  putting  in  the  bread,  and  unless  much  more 
fuel  is  expended  than  is  really  necessary  in  heating  an  oven  upon  this  principle, 
it  becomes  chilled  before  the  loaves  are  all  set  in,  and  they  are,  therefore,  by  this 
means,  very  much  injured. 

To  remedy  this  inconvenience,  many  ovens  have  latterly  been  built  upon  a 
pavement,  supported  upon  solid  brick-work,  with  a door  of  iron,  furnished  with  a 
damper  to  carry  off  the  steam  as  it  rises,  and  heated  with  fossil  coal.  On  one  side 
is  a fire-place  or  furnace,  with  grating,  ash-hole,  and  iron  door,  similar  to  that  for 
supporting  a copper,  with  a partition  to  separate  it  from  the  oven,  and  open  at 
one  end.  Over  this  is  a middling-sized  copper  or  boiler,  with  a cock  at  the 
bottom,  and  on  one  side  of  it  is  placed  the  proving-oven,  the  whole  being  faced 
with  brick  and  plaster. 

When  this  oven  is  required  to  be  heated,  the  boiler  is  filled  with  water,  and, 
the  fire  being  kindled,  the  flame  spreads  around,  in  a circular  direction,  all  over 
its  concavity,  and  renders  it  as  hot  as  if  heated  with  wood,  without  causing  dirt 
or  ill  smell,  while  the  smoke  escapes  through  an  aperture,  which  may  pass  into  the 
kitchen  chimney.  When  the  coal  is  burnt  to  a cinder,  there  is  no  necessity  for 
removing  it,  as  it  prevents  the  oven  from  cooling  while  the  bread  is  setting  in,  and 
keeps  up  a regular  heat  till  the  door  is  closed.  The  advantages  of  an  oven  built 
upon  this  principle  are  too  obvious  to  require  comment. 

Plate  XXXVII.,  in  detail,  is  an  improved  plan  of  an  oven  on  the  new  construc- 
tion. It  has  been  constructed  by  Mr.  Elms,  the  architect,  under  whose  direc- 
tion it  has  been  placed  in  various  public  buildings  in  different  parts  of  Europe. 
Fig.  1 is  the  plan  of  the  oven ; the  fire  is  put  into  the  furnace  A,  and  is 
supported  upon  wrought-iron  bars,  which  are  fixed  an  inch  and  a half  below 
the  level  of  the  oven,  to  prevent  the  cinders  from  entering  it;  the  outside  of 
the  furnace  is  shut  with  two  cast-iron  doors  (1,  2, in  plan);  the  ashes  fall  into  the 
ash-pit  beneath,  B {fig.  2),  the  door  of  which  is  marked  3 in  the  elevation 
{jig.  3).  While  the  coals  are  burning,  the  mouth  of  the  oven  is  inclosed  only  by 
the  curve  cast-iron  door,  or  blower,  B,  shown  in  the  section  of  the  oven  {fig.  4) 
and  elevation  {fig.  10),  and  which  is  so  shaped  in  order  to  make  a proper  pas- 
sage for  the  smoke  to  the  flue,  C ; this  door,  or  blower,  is  not  hung,  but  is  put  up 
and  taken  away  by  hand,  as  may  be  required.  When  the  oven  is  sufficiently 
hot,  the  tender  or  baker  stationed  at  the  mouth,  with  an  iron  bar  {fig.  5), 
slides  the  cast-iron  stopper  D {figs.  1 and  6)  to  the  angle  F,  where  it  stops,  as 


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CONSTRUCTION  OF  OVENS. 


179 


shown  by  the  dotted  line ; then,  going  to  the  mouth  of  the  furnace,  he  hooks  the 
crooked  part  of  the  same  iron  bar  8)  into  the  circular  hole  of  the  stopper  H 
(fig.  7),  and  pulls  the  fillet  (fig.  8)  into  the  frame  of  the  furnace,  upon  which  it 
fits.  This  stopper  is  made  to  slide,  but  not  in  a groove,  as  the  cinders  might 
. sometimes  prevent  its  being  shut.  Fig.  8 represents  an  iron  frame,  to  be  fixed 
round  the  mouth  of  the  inside  of  the  furnace ; the  opening  of  the  mouth  should 
be  one  foot  two  inches  wide,  and  one  foot  high,  and  should  be  made  to  receive 
the  fillets  of  the  stopper. 

The  door,  K {fig.  4),  is  fastened  to  an  iron  chain,  and  is  raised  or  let  down  at 
pleasure  by  turning  the  lever  L (figs.  4 and  10).  In  order  to  prevent  the  heat 
from  escaping  w'hile  the  bread  is  putting  in,  the  mouth  of  the  oven  must  be  made 
as  small  as  possible.  To  the  handle  of  the  lever  is  hung  an  iron  pin,  with  a 
chain,  and  over  it  is  a semicircular  iron  plate,  fastened  to  the  wall,  with  five  holes 
to  receive  the  pin,  by  which  the  height  of  the  door,  K,  may  be  regulated  at 
pleasure. 

When  bread  is  baking,  the  curved  door  B,  not  being  then  wanted,  is  taken 
away ; and  the  tw’o  doors  of  the  oven,  with  the  two  doors  of  the  furnace,  are 
shut  up.  At  the  top  of  the  furnace,  M (fig.  4),  is  a small  flue,  about  three  inches 
square,  communicating  with  the  flue  of  the  oven.  The  use  of  this  small  flue  is 
to  leave  a passage  for  the  sulphur  that  may  remain  in  the  ashes,  and  might  injure 
the  bread  while  baking.  The  communication  of  this  small  flue  of  the  oven  is 
opened  or  shut  by  means  of  an  iron  slider,  N (fig.  10).  Over  the  furnace  is  a 
niche  (fig.  3),  with  a boiler  of  hot  water. 

It  has  been  observed,  that,  in  ovens  with  this  construction  of  the  fire-place,  it  is 
always  proper  to  set  the  bars  eight  or  ten  inches  in  from  the  door ; by  this  means 
a supply  of  coals  will  be  kept  warming  before  they  are  pushed  forward  into  the 
fire.  The  importance  of  this  preparation  is  known  to  those  who  have  attended 
to  the  effect  of  every  fresh  supply  of  coals  to  the  boilers  of  steam-engines,  as  it 
instantly  stops  the  boiling,  unless  this  precaution  is  attended  to.  It  also  prevents, 
in  a great  measure,  the  cold  air  getting  in  between  the  door  and  frame  of  the  fire- 
place, which  frequently  happens,  from  the  difficulty  of  fitting  iron  doors  to  iron 
frames. 

Ovens,  on  the  improved  construction,  will  hold,  according  to  their  size,  as  fol- 
lows: — eight  feet  wide  and  seven  deep,  ten  bushels  of  bread;  nine  feet  wide 
and  seven  and  one  half  feet  deep,  ten  bushels  ; ten  feet  wide  and  eight  and  a 
half  feet  deep,  twelve  bushels. 

Plate  XXXVIII.  This  plate  represents  a baker’s  oven,  heated  by  coal ; this 
oven  has  many  advantages  over  any  other ; its  construction  is  simple,  as  will  be  seen 
by  reference  to  the  plan;  it  economizes  labor,  as,  when  the  oven  is  properly  heated. 


180 


PRACTICAL  MASONRY. 


and  with  a proper  quantity  of  coal  and  a well  regulated  fire,  a tender  stationed  at 
the  mouth  may,  when  the  bottom  of  the  oven  is  covered  with  bread,  begin  to  take 
out  where  he  began  to  set  in,  and  thus  continue  his  labors  as  long  as  he  pleases, 
without  being  obliged,  as  in  other  ovens,  to  stop  and  renew  the  heat  and  clean 
the  bottom ; here  the  heat  and  labor  is  continually  kept  up,  therefore  one  half  of 
the  time  may  be  saved.  This  oven  is  built  of  brick,  as  shown  by  figs.  1, 2,  3,  and  4. 
Fig.  1,  front  elevation ; a,  the  entrance  to  the  cavity  under  the  bottom  ; b,  the  ash- 
pit ; c,  the  door  inclosing  the  grate  ; d,  the  oven-door ; the  doors  and  frames 
made  of  cast-iron  ; in  the  ash-pit  door,  a slide  to  regulate  the  draft  of  air.  Fig.  2 
is  a horizontal  section  at  the  bottom  of  the  oven ; the  darts  show  the  direction  of 
the  heat  and  smoke,  inclosed  by  a sheet-iron  funnel  twelve  inches  perpendicular, 
and  four  inches  on  the  horizontal  line,  leading  from  the  coal-grate  to  the  chimney- 
flue,  around  the  outside  of  the  oven-hearth  ; near  the  entrance  to  the  chimney-flue 
is  a slide  to  retain  the  heat  in  the  funnel  at  pleasure.  Fig.  3,  a horizontal 
section  under  the  hearth ; o,  the  entrance  under  the  hearth ; b,  the  cavity ; 
c,  a centre  pier  to  support  the  bottom  of  the  oven,  scale  four  feet  to  an  inch. 
Fig.  4,  a vertical  section ; a a,  smoke-llue  through  which  the  heat  passes  from 
the  grate  to  the  chimney-flue,  through  sheet-iron  funnel  nearly  surrounding 
the  interior  at  the  bottom,  diffusing  the  heat  into  the  oven  , a space  of  time 
usual  for  the  ordinary  heating  at  first  will  be  all  the  hindrance  for  the  day, 
and  the  tender  then  takes  his  station  at  the  oven-door;  6 6,  cavity  under  the 
bottom  ; c,  the  arch  of  the  oven ; d d,  space  above  the  arch,  generally  filled  in 
with  a portion  of  sand  to  retain  the  heat. 


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ORDERS  OF  ARCHITECTURE. 

''  ' • CHAPTER  VI. 

ORDERS  OF  ARCHITECTURE. 

SECTION  I.  — Grecian  Doric. 

I HAVE  here  made  use  of  the  Grecian  example  given  by  Vitruvius,  from  the 
Temple  of  Minerva,  on  the  Acropolis  at  Athens,  built  under  the  administration  of 
Pericles,  the  representation  of  which  is  found  in  Plate  XXXIX.  Fig.  1,  a section 
of  the  entablature,  showing  the  manner  of  finish  and  the  form  of  the  mouldings 
inside  the  portico.  Plate  XL.,  Jig.  2,  a section  of  the  column  at  both  ends,  with 
twenty  flutes  and  the  manner  of  striking  them  ; divide  the  circumference  into 
twenty  equal  parts ; trace  lines  to  the  centre ; with  the  dividers  draw  a line,  for 
the  circumference  of  the  top,  intersected  by  the  radius  a b ; extend  the  dividers 
from  c to  d,  and,  for  the  circumference  of  the  lower  diameter,  to  g ; and  from  e, 
describe  the  curve  for  the  flute  e f ; and  in  like  manner  for  the  upper  diameter,  as 
shown  by  Plate  XXXlX.,Jig.  2 represents  the  planceir,  with  the  mutules, 

having  three  rows  of  pins,  six  in  each  row,  which  are  said  to  have  arisen  from  the 
idea  of  the  ends  of  rafters  forming  the  roof.  Mg.  4,  the  elevation  of  the  triglyphs, 
containing  two  whole  and  two  half  channels.  Fig.  5 shows  a section  of  the  guttae, 
or  drops,  that  are  formed  under  the  triglyph,  or  under  the  fillet  of  the  architrave. 
Plate  XL.,  Jig.  2,  the  capital  of  column  ; a,  b,  the  annulets  formed  on  the  lower 
part  of  the  ovolo. 

Plate  XL.  Fig.  1,  the  proportional  figures  from  the  scale  of  the  column. 
Divide  the  lower  end  into  two  equal  parts  ; each  is  called  a module ; divide  the 
module  into  thirty  parts,  which  are  called  minutes,  as  figured  on  the  order ; 
under  the  column  H is  the  height  of  each  member,  and  under  the  column  P their 
projections  from  a line  drawn  perpendicular  through  the  centre  of  this  column  ; 
the  entire  height  of  the  order  in  this  example  is  divided  into  eight  parts,  makii  g 
eight  diameters  and  thirty-five  minutes.  Fig.  2,  the  scale  of  diameter.  Fig.  3^ 
the  lower  part  of  the  same.  Fig.  4,  the  whole  height  of  the  order,  the  letters 
on  the  same  are  references  to  the  introduction. 


SECTION  II. — Grecian  Ionic. 

^ Plate  XLI.  Fig.  1,  the  example  from  the  Temple  of  Minerva  Polias,  leaving  the 
ornamented  mouldings  for  those  who  prefer  to  make  use  of  them  in  more  expen- 


182 


PRACTICAL  MASONRY. 


sive  structures.  The  proportional  measures  are  given  on  the  margin  in  height 
and  projections.  Fig.  2,  the  Ionic  base.  Fig.  3,  elevation  of  the  order.  See 
figures  on  the  margin.  This  style  of  base,  the  Attic,  or  the  base  on  pilasters, 
Plate  XlA\.,jig.  1,  may  be  used  as  may  be  most  appropriate  for  the  structure  into 
which  they  are  introduced.  The  Ionic  base  may  be  most  proper  for  common  use. 

Plate  XLII.  Fig.  4,  a pilaster  or  anta  to  the  Ionic  column ; Fig.  2,  the  origi- 
nal cap  figured  in  the  columns  H,  P,  Plate  XLI.,  fig.  1 ; Fig.  3,  base.  See 
figures  for  proportions. 


SECTION  III.  — Grecian  Corinthian. 

This  order  seems  to  have  taken  rise  in  the  flourishing  days  of  Corinth,  a cele- 
brated city  of  Greece.  The  proportions  of  the  order  resemble  the  graceful 
figure  of  a virgin,  more  delicate  than  the  more  mature  age  of  the  matron,  which 
has  given  rise  to  the  Ionic  proportions.  The  composition  of  foliage  is  considered 
the  leading  character  of  the  Corinthian  capital,  which  is  arranged  in  two  annular 
rows  of  leaves,  so  that  each  leaf  in  the  upper  row  grows  up  between  those  of 
the  lower  row,  in  such  a manner  that  a leaf  of  the  upper  row  will  stand  in  the 
middle  of  each  face  of  the  capital,  and  from  each  leaf  of  the  upper  row  three 
stalks  spring  with  volutes,  two  of  them  meeting  under  the  angle  of  the  abacus, 
and  two  in  the  centre  of  the  side,  touching  or  interwoven  with  each  other.  A 
capital  thus  constructed  is  called  Corinthian. 

Plate  XLI  1 1.  This  example  is  from  the  Lantern  of  Demosthenes,  otherwise 
called  the  Monument  of  Lysicrates.  With  some  variation  in  the  entablature  and 
dentils,  it  may  be  considered  a beautiful  specimen  of  the  Grecian  art,  and  may  be 
imitated  with  success  when  elegance  is  required  in  the  composition.  Fig.  1 rep- 
resents the  entablature  and  cap  of  the  column.  Fig.  2,  the  base,  dimensions  of 
height  and  projections  figured  under  P,  H,  from  a scale  of  sixty  minutes  for  the 
diameter  of  the  column  at  the  base.  Fig.  3,  the  full  length  column,  entire  height 
of  the  order. 

Plate  XLIV.  Fig.  1,  a design  for  antae  for  the  columns,  Plate  XLIII.  The 
face  of  this  anta,  or  pilaster,  is  equal  to  the  diameter  of  the  column  at  the  neck,  and 
equal  in  width  at  top  and  bottom ; thus  avoiding  the  difficulty  of  increasing  the 
projection  of  the  capital  beyond  that  of  the  column  to  which  it  may  be  attached. 
Fig.  2,  the  capital  of  column,  Plate  XLIII.,  fig.  1.  Inverted  and  horizontal  sec- 
tion of  the  column  and  flutes  at  the  neck.  Fig.  3,  the  cornice,  inverted. 

The  Romans,  adopting  the  general  features  of  this  order,  introduced  into  it 
some  variations  from  the  Greek  specimens. 


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GLOSSARY 


OF 

ARCHITECTURAL  TERMS. 


Abacus.  The  upper  member  of  the  capital  of  I 
a column  whereon  the  architrave  rests.  Scam-  ; 
mozzi  uses  this  term  for  a concave  moulding  in 
the  capital  of  the  Tuscan  pedestal,  which,  con- 
sidering its  etymology,  is  an  error. 

Abutment.  The  solid  part  of  a pier  from 
which  an  arch  springs. 

Acanthus.  A plant  called  in  English  Bear's  j 
Breech.,  whose  leaves  are  employed  for  decorat-  i 
ing  the  Corinthian  and  Composite  capitals.  The 
leaves  of  the  acanthus  are  used  on  the  bell  of  the 
capital,  and  distinguish  the  two  rich  orders  from 
the  three  others. 

Accompaniments.  Buildings,  or  ornaments, 
having  a necessary  connection  or  dependence,  and  j 
which  serve  to  make  a design  more  or  less  com-  ■ 
plete;  a characteristic  peculiarity  of  ornaments. 

Accouplement.  Among  carpenters,  a tie  or 
brace  ; sometimes  the  entire  work  when  framed. 

Acroteria.  The  small  pedestals  placed  on 
the  extremities  and  apex  of  a pediment. 

Admeasurement.  Adjustment  of  proportions  ; 
technically,  an  estimate  of  the  quantity  of  ma- 
terials and  labor  of  any  kind  used  in  a building. 

Alcove.  The  original  and  strict  meaning  of 
this  word,  which  is  derived  from  the  Spanish 
alcoba,  is  that  part  of  a bed-chamber  in  which 
the  bed  stands,  and  is  separated  from  the  other 
parts  of  the  room  by  columns  or  pilasters. 

Amphiprostyle.  In  ancient  architecture,  a 
temple  with  columns  in  the  rear  as  well  as  in  the 
front. 

Amphitheatre.  A double  theatre,  of  an  ellip- 
tical form  on  the  ground  plan,  for  the  exhibition 
of  the  ancient  gladiatorial  fights  and  other  shows. 

Ancones.  The  consoles  or  ornaments  cut  on 
the  keys  of  arches,  sometimes  serving  to  support 
busts  or  other  figures. 

Annulet.  A small  square  moulding,  which 
crowns  or  accompanies  a larger.  Also,  that  fillet 


which  separates  the  flutings  of  a column.  It  is 
sometimes  called  a List,  or  Listella,  which  see. 

Antce.  A name  given  to  pilasters  attached  to 
a wall. 

Apophyge.  That  part  of  a column  between 
the  upper  fillet  of  the  base  and  the  cylindrical 
part  of  the  shaft  of  the  column,  which  is  usually 
curved  into  it  by  a cavetto. 

Arceostyle.  That  style  of  building  in  which 
the  columns  are  distant  four,  and  sometimes  five, 
diameters  from  each  other;  but  the  former  is  the 
proportion  to  which  the  term  is  usually  applied. 
This  columnar  arrangement  is  suited  to  the  Tus- 
can order  only. 

Arcade.  A series  of  arches,  of  apertures,  or 
recesses,  a continued  covered  vault,  or  arches 
suj)ported  on  piers  or  columns  instead  of  galler- 
ies. In  Italian  towns,  the  streets  are  lined  with 
j arcades  like  those  of  Covent  Garden  and  the 
Royal  Exchange. 

Arch.  An  artful  arrangement  of  bricks,  stones, 
or  other  materials,  in  a curvilinear  form,  which, 
by  their  mutual  pressure  and  support,  perform 
the  office  of  a lintel,  and  carry  superincumbent 
weights,  — the  whole  resting  at  its  extremities 
upon  piers  or  abutments. 

Arch-buttress,  or  Flying-buttress,  (in  Gothic 
architecture,)  an  arch  springing  from  a buttress 
or  pier,  and  abutting  against  a wall. 

Archeion.  The  most  retired  and  secret  place 
in  Grecian  temples,  used  as  a treasury,  wherein 
were  deposited  the  richest  treasures  pertaining  to 
the  deity  to  whom  the  temple  was  dedicated. 

Architect.  One  who  designs  and  superintends 
the  erection  of  buildings. 

Architrave.  The  lower  of  the  primary  di- 
visions of  the  entablature.  It  is  placed  imme- 
diately upon  the  abacus  of  the  capital. 

Astragal.  From  the  Greek  word  for  a bone 
in  the  foot,  to  which  this  moulding  was  supposed 


184 


GLOSSARY  OF  ARCHITECTURAL  TERMS. 


to  bear  a resemblance.  A small  moulding, 
whose  profile  is  semicircular,  and  which  bears 
also  the  name  of  Talon,  or  Tondino.  The  astra- 
gal is  often  cut  into  beads  and  berries,  and  used 
in  ornamental  entablatures  to  separate  the  faces 
of  the  architrave. 

Attic.  A term  that  expresses  any  thing  invent- 
ed or  much  used  in  Attica,  or  the  city  of  Athens. 
A low  story  erected  over  an  order  of  architecture, 
to  finish  the  upper  part  of  the  building,  being 
chiefly  used  to  conceal  the  roof,  and  give  greater 
dignity  to  the  design. 

Attic  Base.  See  Base. 

Attic  Order.  An  order  of  low  pilasters,  gen- 
erally placed  over  some  other  order  of  columns. 
It  is  improperly  so  called,  for  the  arrangement 
can  scarcely  be  called  an  order. 

Auriel,  or  Oriel,  (in  Gothic  architecture,)  a 
window  projecting  outwards  for  private  confer- 
ence : whence  its  appellation. 

Balcony.  A projection  from  the  surface  of  a 
wall,  supported  by  consoles  or  pillars,  and  sur-  , 
rounded  by  a balustrade. 

Baluster.  A small  pillar,  or  pilaster,  serving 
to  support  a rail.  Its  form  is  of  considerable 
variety,  in  different  examples.  Sometimes  it  is 
round,  at  other  times  square  ; it  is  adorned  with 
mouldings  and  other  decorations,  according  to 
the  richness  of  the  order  it  accompanies. 

Balustrade.  A connected  range  of  a number 
of  balusters  on  balconies,  terraces  around  altars, 
Ac.  See  Baluster. 

Band.  A term  used  to  express  what  is  gen- 
erally called  a Face,  or  Facia.  It  more  properly 
means  a flat,  low,  square-pr^led  member,  with- 
out respect  to  its  place.  Tliat  from  which  the 
Corinthian  or  other  modillions,  or  the  dentils,  pro- 
ject, is  called  the  modillion  band,  or  the  dentil 
band,  as  the  case  may  be. 

Bandelet.  A diminutive  of  the  foregoing  term, 
used  to  express  any  narrow  flat  moulding.  The 
tajniaon  the  Doric  architrave  is  called  its  bandelet. 

Banker.  A stone  bench  on  which  masons  cut 
and  square  their  work. 

Banquet.  The  foot-way  of  a bridge  raised 
above  the  carriage-w’ay. 

Barrel  Drain.  A drain  of  the  form  of  a hol- 
low cylinder. 

Base.  The  lower  part  of  a column,  moulded 
or  plain,  on  which  the  shaft  is  placed. 

Basement.  The  lower  part  or  story'  of  a build- 
ing, on  which  an  order  is  placed,  with  a base  or 
plinth,  die,  and  cornice. 

Basil.  A word  used  by  carpenters,  &c.,  to 
denote  the  angle  to  which  any  edge-tool  is  ground 
and  fitted  for  cutting  wood,  Ac. 

Basin,  en  Coquille,  that  is,  shaped  like  a shell. 


Basin  is  likewise  used  for  a dock. 

Basket.  A kind  of  vase  in  the  form  of  a 
basket  filled  with  flowers  or  fruits,  serving  to  ter- 
minate some  decoration. 

Bassilica.  A town  or  court-hall,  a cathedral, 
a palace,  where  kings  administer  justice. 

Basso-relievo,  or  Bass-relief.  The  represent- 
ation of  figures  projecting  from  a back-ground, 
without  being  detached  from  it.  Though  this 
word,  in  general  language,  implies  all  kinds  of 
relievos,  from  that  of  coins  to  more  than  one 
half  of  the  thickness  from  the  back-ground. 

Bath.  A receptacle  of  water  appropriated  for 
the  purpose  of  bathing. 

Batten.  A scantling  of  stuff,  from  two  to  six 
inches  broad,  and  from  five  eighths  to  two  inches 
thick,  used  in  the  boarding  of  floors  ; also  upon 
walls,  in  order  to  secure  the  lath  on  which  the 
plaster  is  laid. 

Batter.  When  a wall  is  built  in  a direction 
that  is  not  perpendicular. 

Battlements.  Indentations  on  the  top  of  a 
parapet,  or  wall,  first  used  in  ancient  fortifica- 
tions ; and  afterw’ards  applied  to  churches  and 
other  buildings. 

Bay,  (in  Gothic  architecture,)  an  opening  be- 
tween piers,  beams,  or  mullions. 

Bay  Window.  See  Auriel. 

Bead  and  Flush  Work.  A piece  of  panel- 
work,  with  a bead  run  on  each  edge  of  the  in- 
cluded panel. 

Bead  and  Butt  Work.  A piece  of  framing  in 
which  the  panels  are  flush,  having  beads  stuck  or 
run  upon  the  two  edges,  with  the  grain  of  the 
wood  in  their  direction. 

Bed-Mouldings.  Those  mouldings  in  all  the 
orders  between  the  corona  and  frieze. 

Billet-Moulding,  (in  Gothic  architecture,)  a 
cylindrical  moulding,  discontinued  and  renewed 
at  regular  intervals. 

Boltel,  (in  Gothic  architecture,)  slender  shafts, 
whether  arranged  round  a pier,  or  attached  to 
doors,  windows,  &c.  The  term  is  also  used  for 
any  cylindrical  moulding. 

Boss,  (in  Gothic  architecture,)  a sculptured 
protuberance  at  the  inteijunction  of  the  ribs  in  a 
vaulted  roof. 

Boss  age.  (A  French  term.)  Any  projection 
left  rough  on  the  face  of  a stone  for  the  purpose  of 
sculpture,  which  is  usually  the  last  thing  finished. 

Boultin.  A name  given  to  the  moulding, 
called  the  egg  or  quarter-round. 

Broach,  (in  Gothic  architecture,)  a spire,  or 
polvgonal  pyramid,  whether  of  stone  or  timber. 

Bracket,  (in  Gothic  architecture,)  a projection 
to  sustain  a statue,  or  other  ornament ; and  some- 
times supporting  the  ribs  of  a roof. 


GLOSSARY  OF  ARCHITECTURAL  TERMS. 


185 


Bulk.  A piece  of  timber  from  4 to  10  inches 
square,  and  is  sometimes  called  ranging  timber. 

Buttress,  (in  Gothic  architecture*)  a projection 
on  the  exterior  of  a wall,  to  strengthen  the  piers 
and  resist  the  pressure  of  the  arches  within. 

Cahling.  The  filling  up  of  the  lower  part  of 
the  fluting  of  a column  with  a solid  cylindrical 
piece.  Flutings  thus  treated  are  said  to  be  cabled. 

Caisson.  A name  given  to  the  sunk  panels  of 
various  geometrical  forms,  symmetrically  dispos- 
ed in  flat  or  vaulted  ceilings,  or  in  soffits,  gener- 
ally. 

Canopy,  (in  Gothic  architecture,)  the  orna- 
mented drip-stone  of  an  arch.  It  is  usually  of  the 
ogee  form. 

Canted  (in  Gothic  architecture.)  Any  part  of 
a building  having  its  angles  cut  off,  is  said  to  be 
canted. 

Capital.  The  head  or  uppermost  part  of  a 
column  or  pilaster. 

Carpenter.  An  artificer  whose  business  is  to 
cut,  fashion,  and  join  timbers  together,  and  other 
wood  for  the  purpose  of  building;  tlie  word  is 
from  the  French  charpentier,  derived  from  char- 
peiitie,  which  signifies  timber. 

Carpentry,  or  that  branch  which  is  to  claim 
our  attention,  is  divided  into  three  principal  heads, 
viz..  Constructive,  Descriptive,  and  Mechanical ; 
of  these.  Descriptive  carpentry  shows  the  lines 
or  methods  for  forming  every  sj)ecies  of  work  in 
piano,  by  the  rules  of  geometry  ; Constructive 
carpentry,  the  practice  of  reducing  the  wood  into 
particular  forms,  and  joining  the  forms  so  produc- 
ed, so  as  to  make  a complete  whole,  according  to 
the  intention  of  the  design  ; and  Mechanical  car- 
pentry displays  the  relative  strength  of  the  tim- 
bers, and  the  strains  to  which  they  are  subjected 
by  their  disposition. 

Cartouch.  The  same  as  modillions,  except 
that  it  is  exclusively  used  to  signify  those  blocks 
or  modillions  at  the  eaves  of  a house.  See  Mo- 
dill  ion. 

Caryatides.  Figures  of  women,  which  serve 
instead  of  columns  to  support  the  entablature. 

Casement.  The  same  as  Scotia,  which  see. 
The  term  is  also  used  for  a sash  hung  upon  hinges. 

Cauliculus.  The  volute  or  twist  under  the 
flower  in  the  Corinthian  capital. 

Cavetto.  A hollow  moulding,  whose  profile 
is  a quadrant  of  a circle,  principally  used  in  cor- 
nices. 

Cell.  See  Naos. 

Cincture.  A ring,  list,  or  fillet,  at  the  top  or 
bottom  of  a column,  serving  to  divide  the  shaft 
of  the  column  from  its  capital  and  base. 

Chamfer,  ( in  Gothic  architecture,)  an  arch,  or 
jamb  of  a door,  canted. 


Chanip,  (in  Gothic  architecture,)  a flat  surface 
in  a wall  or  pier,  as  distinguished  from  a moulding, 
shaft,  or  panel. 

Cinque-foil,  (in  Gothic  architecture,)  an  orna- 
mental figure  with  five  leaves  or  points. 

Column.  A member  in  architecture  of  a cylin- 
drical form,  consisting  of  a base,  a shaft  or  body, 
and  a capital.  It  differs  from  the  pilaster,  which 
is  square  on  the  plan.  Columns  should  always 
stand  perpendicularly. 

Composite  Order.  One  of  the  orders  of  ar- 
chitecture. 

Cope,  Coping,  (in  Gothic  architecture,)  the 
stone  covering  the  top  of  a wall  or  parapet. 

Corhel,  (in  Gothic  architecture,)  a kind  of 
bracket.  The  term  is  generally  used  for  a con- 
tinued series  of  brackets  on  the  exterior  of 
a building,  supporting  a projecting  battlement, 
which  is  called  a Corhel  table. 

Corinthian  Order.  One  of  the  orders  of  ar- 
chitecture. 

Cornice.  The  projection  consisting  of  several 
members  which  crowns  or  finishes  an  entablature, 
or  the  body  or  part  to  which  it  is  annexed.  The 
cornice  used  on  a [)edcstal  is  called  the  cap  of 
the  pedestal. 

Corona  is  that  flat,  square,  and  massy  mem- 
ber of  a cornice,  more  usually  called  the  drip  or 
larmier,  whose  situation  is  between  the  cymatium 
above,  and  the  bed -moulding  below.  Its  use  is  to 
carry  the  water,  drop  by  drop,  from  the  building. 

Corridor.  A gallery  or  open  communication 
to  the  diflerent  apartments  of  a house. 

Corsa.  The  name  given  by  Vitruvius  to  a 
platband  or  square  facia,  whose  height  is  more 
than  its  projecture. 

Crenelle,  (in  Gothic  architecture,)  the  opening 
of  an  embattled  parapet. 

Crest,  (in  Gothic  architecture,)  a crowning 
ornament  of  leaves  running  on  the  top  of  a 
screen,  or  other  ornamental  work. 

Crocket,  (in  Gothic  architecture,)  an  ornament 
of  leaves  running  up  the  sides  of  a gable,  or  or- 
namented canopy. 

Cupola.  A small  room,  either  circular  or  poly- 
gonal, standing  on  the  top  of  a dome.  By  some 
it  is  called  a lantern. 

Cushioned.  See  Frieze. 

Cusp,  (in  Gothic  architecture,)  a name  for  the 
segments  of  circles  forming  the  trefoil,  quatre- 
foil,  &c. 

Cyma,  called  also  Cymatium,  its  name  arising 
from  its  resemblance  to  a wave.  A moulding 
which  is  hollow  in  its  upper  part,  and  swelling 
below. 

Decagon.  A plain  figure,  having  ten  sides 
and  angles. 


24 


186 


GLOSSARY  OF  ARCHITECTURAL  TERMS. 


Decastyle.  A building  having  ten  columns  in 
front. 

Decempeda.  {Decern,  ten,  and  pes,  foot,  Lat.) 
A rod  of  ten  feet  used  by  the  ancients  in  measur- 
ing. It  was  subdivided  into  twelve  inches  in  each 
foot,  and  ten  digits  in  each  inch ; like  surveyors’ 
rods  used  in  measuring  short  distances,  &c. 

Decimal  Scale.  Scales  of  this  kind  are  used 
by  draftsmen,  to  regulate  the  dimensions  of  their 
drawings.  I 

Decoration.  Any  thing  that  enriches  or  gives 
beauty  and  ornament  to  the  orders  of  architecture. 

Demi-Metope.  The  half  a metope,  which  is 
found  at  the  retiring  or  projecting  angles  of  a 
Doric  frieze. 

Dentils.  Small  square  blocks  or  projections 
used  in  the  bed-mouldings  of  the  cornices  in 
the  Ionic,  Corinthian,  Composite,  and  sometimes 
Doric  orders. 

Details  of  an  Edifice.  Drawings  or  delinea-  I 
tions  for  the  use  of  builders,  otherwise  called  ^ 
working  plans.  j 

Diagonal  Scale  is  a scale  subdivided  into  | 
smaller  parts  by  secondary  intersections  or  ob- 
lique lines. 

Diameter.  The  line  in  a circle  passing  from  i 
the  circumference  through  the  centre.  i 

Diamond.  A sharp  instrument  formed  of  that  ; 
. precious  stone  and  used  for  cutting  glass.  ' 

Diapered  (in  Gothic  architecture).  A panel, or  ' 
other  flat  surface,  sculptured  with  flowers,  is  said  j 
to  be  diapered. 

Diashjle.  That  intercolumniation  or  space  be- 
tween columns,  consisting  of  three  diameters  ; — ! 
some  say  four  diameters.  I 

Die,  or  Dye.  A naked,  square  cube.  Thus  1 
the  body  of  a pedestal,  or  that  part  between  its  ' 
base  and  cap,  is  called  the  die  of  the  pedestal.  | 
Some  call  the  abacus  the  die  of  the  capital.  ' 

Dimension.  {Dimetier,  Lat  ) In  geometry  is 
either  length,  breadth,  or  thickness. 

Diminution.  A term  expressing  the  gradual  , 
decrease  of  thickness  in  the  upper  part  of  a 
column. 

Dipteral.  A term  used  by  the  ancici 
press  a temple  with  a double  range  of 
in  each  of  its  flanks. 

Dodecagon.  A regular  polygon,  with  twelve 
equal  sides  and  angles. 

Dodecastyle.  A building  having  twelve  col- 
umns in  front. 

Dome.  An  arched  or  vaulted  roof  springing 
from  a polygonal,  circular,  or  elliptic  plane. 

Doric  Order.  One  of  the  five  orders  of  ar- 
chitecture. 

Dormant,  or  Dormer  Windoir,  (in  Gothic  ar- 
chitecture,) a window  set  upon  the  slope  of  a roof 
or  spire. 


ts  to  ex- 
columns 


Dooks.  Flat  pieces  of  wood  of  the  shape  and 
size  of  a brick,  inserted  in  brick  walls,  sometimes 
called  plugs  or  wooden  bricks. 

Door.  The  gate  or  entrance  of  a house,  or 
other  building,  or  of  an  apartment  in  a house. 

Dormitory.  A sleeping-room. 

Drawing,  or  Withdrawing- Room.  A large 
and  elegant  apartment,  into  which  the  company 
withdraw  after  dinner. 

Dressing-Room.  An  apartment  contiguous 
to  the  sleeping-room,  for  the  convenience  of 
dressing. 

Drip,  (in  Gothic  architecture,)  a moulding 
much  resembling  the  cymatium  of  Roman  archi- 
tecture, and  used  for  the  same  purpose  as  a 
canopy  over  the  arch  of  a door  or  window. 

Drops.  See  Gnttce. 

Echinus.  The  same  as  the  ovolo  or  quarter- 
round  ; but  perhaps  it  is  only  called  echinus 
with  propriety. 

Edging.  The  reducing  the  edges  of  ribs  or 
rafters,  that  they  may  range  together. 

Elbows  of  a Window.  The  two  panelled 
flanks,  one  under  each  shutter. 

Elevation.  A geometrical  projection  drawn 
on  a plane,  perpendicular  to  the  horizon. 

Embankments  are  artificial  mounds  of  earth, 
stone,  or  other  materials,  made  to  confine  rivers, 
canals,  and  reservoirs  of  water  within  their  pre- 
scribed limits ; also  for  levelling  up  of  rail- 
roads, Ac. 

Emltrasure,  (in  Gothic  architecture,)  the  same 
as  Crenelle,  which  see. 

Encarpus.  The  festoons  on  a frieze,  consist- . 
ing  of  fruits,  flow'ers,  and  leaves.  See  Festoon. 

Entablature.  The  assemblage  of  parts  sup- 
ported by  the  column.  It  consists  of  three  parts, 
the  architrave,  frieze,  and  cornice. 

Entail,  (in  Gothic  architecture,)  delicate  can'- 
ing. 

Entasis.  The  slight  curvature  of  the  shafts 
of  ancient  Grecian  columns,  particularly'  the 
Doric,  which  is  scarcely  perceptible,  and  beauti- 
fully graceful. 

Entresol.  See  Mezzanine. 

Epistylum.  The  same  as  Architrave,  which 
see. 

Eusiyle.  That  intercolumniation,  which,  as  its 
name  would  import,  the  ancients  considered  the 
most  elegant,  namely,  two  diameters  and  a quarter 
of  a column.  Vitruvius  says  this  manner  of  ar- 
ranging columns  exceeds  all  others  in  strength, 
convenience,  and  beauty. 

Fagade.  The  face  or  front  of  any  considerable 
building  to  a street,  court,  garden,  or  other  place. 

Facia.  A flat  member  in  the  entablature  or 
elsewhere,  being  in  fact  nothing  more  than  a band 
or  broad  fillet. 


GLOSSARY  OF  ARCHITECTURAL  T E R xM  S . 


187 


Fa/ie,  Phane,  Vane,  (in  Gothic  architecture,) 
a plate  of  metal,  usually  cut  into  some  fantastic 
form,  and  turning  on  a pivot,  to  determine  the 
course  of  the  wind. 

Fastigium.  See  Pediment. 

Feather-edged  Boards  are  narrow  boards 
made  thin  on  one  edge.  They  are  used  for  the 
facings  or  boarding  of  wooden  walls. 

Festoon.  An  ornament  of  carved  work,  rep- 
resenting a wreath  or  garland  of  flowers  or  leaves, 
or  both,  interwoven  with  each  other. 

Fillet.  The  small,  square  member,  which  is 
placed  above  or  below  the  various  square  or 
curved  members  in  an  order. 

Finial,  (in  Gothic  architecture,)  the  ornament, 
consisting  usually  of  four  crockets,  which  is  em- 
ployed to  finish  a pinnacle,  gable,  or  canopv. 

Flank.  The  least  side  of  a pavilion,  by  which 
it  is  joined  to  the  main  building. 

Flatning,  in  inside  house-painting,  is  the  mode 
of  finishing  without  leaving  a gloss  on  the  surface, 
which  is  done  by  adding  the  spirits  of  turj)entine 
to  unboiled  linseed  oil. 

Flight  of  Stairs  is  a series  of  steps,  from  one 
landing-place  to  another. 

Floors.  'J'hc  bottom  of  rooms. 

Flulings.  Tlie  vertical  channels  on  the  shafts 
of  columns,  which  are  usually  rounded  at  the  top 
and  bottom. 

Flyers  are  steps  in  a scries,  which  are  parallel 
to  each  other. 

Folding- Doors  are  made  to  meet  each  other 
from  op])osite  jambs,  on  which  they  arc  hung. 

Foliage.  .\n  ornamental  distribution  of  leaves 
or  flowers  on  various  parts  of  the  building. 

Foreshorten.  term  applicable  to  the  draw- 
ings or  designs  in  which,  from  the  obliquity  of 
the  view,  the  object  is  re|)resented  as  receding 
from  the  o[»posite  side  of  the  plane  of  the  pro- 
jection. 

Foundation.  That  part  of  a building  or  wall 
which  is  below  the  surface  of  the  ground. 

Foot.  A measure  of  twelve  inches,  each  inch 
being  three  barleycorns. 

Frame.  The  name  given  to  the  wood-work  of 
windows,  inclosing  glass,  and  the  outward  work 
of  doors  or  windows,  or  window-shutters,  inclos- 
ing panels;  and  in  carpentry,  to  the  timber-work 
supporting  floors,  roofs,  ceilings,  or  to  the  inter- 
secting pieces  of  timbers  forming  partitions. 

Fret.  A kind  of  ornamental  work,  which  is 
laid  on  a plane  surface  ; the  Greek  fret  is  formed 
by  a series  of  right  angles  or  fillets,  of  various 
forms  and  figures. 

Frieze,  or  Frize.  The  middle  member  of  the 
entablature  of  an  order,  which  separates  the  ar- 
chitrave and  the  cornice. 


Frontispiece.  The  face  or  fore  front  of  a 
house  ; but  it  is  a term  more  usually  applied  to 
its  decorated  entrance. 

Fro7it.  A name  given  to  the  principal  interior 
facade  of  a building. 

Frustum.  A piece  cut  ofi'  from  a regular 
figure  ; the  frustum  of  a cone  is  the  part  that  re- 
mains when  the  top  is  cut  ofi’  by  an  intersection 
parallel  to  its  base,  as  the  Grecian  Doric  column 
without  a base. 

Furrings  are  flat  pieces  of  timber,  plank,  or 
board,  used  by  carpenters  to  bring  dislocated 
work  to  a regular  surface. 

Fust.  The  shaft  of  a column.  See  Shaft. 

Gahle,  (in  Gothic  architecture,)  the  triangu- 
larly-headed wall  which  covers  the  end  of  a roof. 

Gable  Window,  (in  Gothic  architecture,)  a 
window  in  a gable.  These  are  generally  the  larg- 
est windows  in  the  composition,  frequentl)^  oc- 
cupying  nearly  the  whole  space  of  the  wall. 

Gablet,  (in  Gothic  architecture,)  a little  gable. 
See  Canopy. 

Gauge.  In  carpentry,  an  instrument  to  strike 
a line  parallel  to  the  straight  side  of  any  board 
or  j)iece  of  stuff. 

Gain.  The  bevelled  shoulder  of  a binding  ■ 
joist.  ^ 

Gai-land,  (in  Gothic  architecture,)  an  orna-* 
mental  band  surrounding  the  top  of  a tower  or 
sjiiro. 

Glyphs.  The  vertical  channels  sunk  in  the 
triglyphs  of  the  Doric  frieze. 

Gola,  or  Gala.  The  same  as  Ogee,  which 
see. 

Gorge.  The  same  as  Cavetto,  which  see. 

Gouge.  A chisel  of  a semicircular  form. 

Granite.  A genus  of  stone  much  used  in 
building,  composed  chiefly  of  quartz,  feldspar, 
and  mica,  forming  rough  and  large  masses  of 
very  great  hardness. 

Groin,  (in  Gothic  architecture,)  the  diagonal 
line  formed  by  the  intersection  of  two  vaults  in  a 
roof. 

Groined  Ceiling.  A surface  formed  of  fliree 
or  more  curved  surfaces,  so  that  every  two  may 
form  a groin,  all  the  groins  terminating  at  one 
e.vtremity  in  a common  point. 

Groove,  or  Mortise.  The  channel  made  by  a 
joiner’s  plane  in  the  edge  of  a moulding,  stile, 
or  rail,  to  receive  the  tenon. 

Ground  Floor.  The  lowest  story  of  a building. 

Ground  Plane.  A line  forming  the  ground  of 
a design  or  picture,  which  line  is  a tangent  to  the 
surface  of  the  face  of  the  globe. 

Ground  Plot.  The  ground  on  which  a build- 
ing is  |)laced. 

Grounds.  Joiners  give  this  name  to  narrow 


I 


188 


GLOSSARY  OF  ARCHITECTURAL  TERMS. 


strips  of  wood  put  in  walls  to  receive  the  laths 
and  plastering. 

Gut  1(2,  or  Drops.  Those  frusta  of  cones  in 
the  Doric  entablature  which  occur  in  the  archi- 
trave below  the  taenia  under  each  triglyph. 

Gutters  are  a kind  of  canals  in  the  roofs  of 
houses,  to  receive  and  carry  off  rain-water. 

Halvi’ig.  The  junction  of  two  pieces  of  tim- 
ber, by  inserting  one  into  the  other  ; in  some  cases 
to  be  preferred  to  mortising. 

Hand-railing.  The  art  of  forming  hand-rails 
round  circular  and  elliptic  well-holes  without  the 
use  of  the  cylinder. 

Hanging-Stile  of  a Door  is  that  to  which  the 
hinges  are  fixed. 

Heel  of  a Rafter.  The  end  or  foot  that  rests 
upon  the  wall-plate. 

Helical  Line  of  a Hand-rail.  The  line,  or 
spiral  line,  representing  the  form  of  the  hand-rail 
before  it  is  moulded. 

Helix.  The  curling  stalk  under  the  flower  in 
the  Corinthian  capital.  See  Cauliculus. 

Hern.  The  spiral  projecting  part  of  the  Ionic 
capital. 

Hexastyle.  A building  having  six  columns  in 
front. 

Hood-mould  (in  Gothic  architecture).  See 
Drip. 

Hook-pins.  The  same  as  Draw  Bore-pins,  \o 
keep  the  tenons  in  their  place,  while  in  the  pro- 
gress of  framing ; the  pin  has  a head  or  notch 
in  the  outer  end  to  draw  it  at  pleasure. 

Hypcethral.  Open  at  top ; uncovered  by  a roof. 

Hyperthyron.  The  lintel  of  a doorway. 

Hypotracheliurn.  A term  given  by  Vitruvius 
to  the  slenderest  part  of  the  shaft  of  a column 
where  it  joins  the  capital.  It  signifies  the  part 
under  the  neck. 

Inchnography.  The  transverse  section  of  a 
building,  which  represents  the  circumference  of 
the  whole  edifice  ; the  different  rooms  and  apart- 
ments, with  the  thickness  of  the  walls  ; the  dimen- 
sions and  situation  of  the  doors,  windows,  chim- 
neys ; the  projection  of  columns,  and  every  thing 
that  could  be  seen  in  such  a section,  if  really 
made  in  a building. 

Impost.  The  layer  of  stone  or  wood  that 
crowns  a door-post  or  pier,  and  which  supports 
the  base  line  of  an  arch  or  arcade  ; it  generally 
projects,  and  is  sometimes  formed  of  an  assem- 
blage of  mouldings. 

Inch.  The  twelfth  part  of  a foot.  For  the  pur- 
pose of  reckoning  in  decimal  fractions,  it  is  divid- 
ed into  ten  parts  or  integers. 

Inclined  Plane.  One  of  the  mechanical  pow- 
ers, used  for  raising  ponderous  bodies,  in  many 
instances  of  immense  weight ; a declivity  of  a 
hill,  &c. 


Insular  Column  is  a column  standing  by  itself. 

Insulated.  Detached  from  another  building. 

Intaglio.  Any  thing  with  figures  in  relief 
on  it. 

Intercolumniation.  The  distance  between  two 
columns. 

Intrados.  The  under  curved  surface  or  soffit 
of  an  arch. 

Inverted  Arches.  Such  as  have  their  intrados 
below  the  centre  or  axis. 

Ionic  Order.  One  of  the  orders  of  architec- 
ture. 

Jack  Plane.  A plane  about  18  inches  long, 
to  prepare  for  the  trying  plane. 

Jack  Rafters.  The  jack  timbers,  which  are 
fastened  to  the  hip  rafters  and  the  wall-plates. 

Jambs.  The  side  pieces  of  any  opening  in  a 
wall,  which  bear  the  piece  that  discharges  the 
superincumbent  weight  of  such  wall. 

Joinery,  in  building,  is  confined  to  the  nicer 
and  more  ornamental  parts. 

Jointer.  A tool  used  for  straightening  and 
preparing  stufT  for  joints,  Ac.  This  jointer  is 
about  two  feet  eight  or  ten  inches  long. 

Kerf.  The  slit  or  cut  in  a piece  of  timber,  or 
in  a stone,  by  a saw. 

King  Post.  The  middle  post  in  a section  of 
rafters. 

Label,  (in  Gothic  architecture,)  a name  for  the 
drip  or  hood-moulding  of  an  arch  when  it  is  re- 
turned square. 

Lacunar,  or  Laquear.  The  same  as  Soffit. 

Lantern,  (in  Gothic  architecture,)  a turret  or 
tower  placed  above  a building,  pierced  either 
with  windows  to  admit  light,  or  holes  to  let  out 
.steam. 

Larmier.  Called  also  Corona,  which  see. 

Lath.  A narrow  slip  of  wood  to  inches 
wide,  to  f inch  thick,  and  four  feet  long,  used 
in  plastering. 

Leaves.  Ornaments  representing  natural  leaves. 
The  ancients  used  two  sorts  of  leaves,  natural  and 
imaginary'.  The  natural  were  those  of  the  laurel, 
palm,  acanthus,  and  olive ; but  they  took  such 
liberties  in  the  form  of  these,  that  they  might 
almost  be  said  to  be  imaginary,  too. 

Level.  A surface  which  inclines  to  neither 
side. 

Lining.  Covering  for  the  interior,  as  casing 
is  covering  the  exterior  surface  of  a building. 

Lintel.  A piece  of  timber  or  stone  placed 
horizontally  over  a door,  window,  or  other  open- 
ing. 

List  or  Listel.  The  same  as  fillet,  or  annulet. 

Listing.  The  cutting  the  sap-wood  out  from 
both  edges  of  a board. 

Loop,  (in  Gothic  architecture,)  a small  narrow 
window. 


GLOSSARY  OF  ARCHITECTURAL  TERMS. 


189 


Louvre  (in  Gothic  architecture).  See  Lan- 
tern. *. 

Luffer  Boarding.  The  same  as  blind  slats. 

Machicolations,  (in  Gothic  architecture,)  small 
openings  in  an  embattled  parapet,  for  the  dis- 
charge of  missile  weapons  upon  the  assailants. 
Frequently  these  openings  are  underneath  the 
parapet,  in  which  case  the  whole  is  brought  for-  ' 
ward  and  supported  by  corbels. 

Mechanical  Carpentry.  That  branch  of  car- 
pentry which  teaches  the  disposition  of  the  tim- 
bers according  to  their  relative  strength,  and  the 
strains  to  which  they  are  subjected. 

Mediceval  Architecture.  The  architecture  of 
England,  France,  Germany,  &c.,  during  the 
Middle  Ages,  including  the  Norman  and  early 
Gothic  styles. 

Members.  {Membrum,  Lat.)  The  different  parts 
of  a building;  the  different  parts  of  an  entabla- 
ture ; the  different  mouldings  of  a cornice,  Ac. 

Metope.  The  square  space  between  two  tri- 
glyphs  of  the  Doric  order.  It  is  sometimes  left 
plain,  at  other  times  decorated  with  sculpture. 

Mezzanine.  A low  story  introduced  between 
two  principal  stories. 

Minerva  Polios.  A Grecian  temple  at  Athens. 

Minute.  The  sixtieth  part  of  the  diameter  of 
a column.  It  is  the  subdivision  by  which  archi- 
tects measure  the  small  parts  of  an  order. 

Mitre.  .-\n  angle  of  forty-five  degrees,  a half 
of  a right  angle. 

Modillion.  An  ornament  in  the  entablature 
of  richer  orders  resembling  a bracket. 

Module.  The  semi-diameter  of  a column. 
This  term  is  only  properly  used  when  speaking 
of  the  orders.  As  a semi-diameter  it  consists  of 
only  thirty  minutes.  See  Minute. 

Mosaic.  A kind  of  painting  representing 
cubes  of  glass,  Ac.,  and  is  formed  of  different 
colored  stones,  for  paving,  Ac.  Specimens  of 
this  kind  have  been  found  among  the  ruins  of 
antiquity. 

Mouldings.  Those  parts  of  an  order  which 
are  shaped  into  various  curved  or  square  forms. 

Mouth.  The  same  as  Cavetto,  which  see. 

Mulule.  A projecting  ornament  of  the  Doric 
cornice  which  occupies  the  place  of  the  modillion 
in  imitation  of  the  ends  of  rafters. 

Mullion,  (in  Gothic  architectu^-e,)  the  frame- 
work of  a window. 

Naked.  The  unornamented  plain  surface  of  a 
wall,  column,  or  other  part  of  a building. 

Naos,  or  Celia.  The  part  of  a temple  within 
the  walls. 

Newel.  The  solid,  or  imaginary  solid,  when 
the  stairs  are  open  in  the  centre,  round  which  the 
steps  are  turned  about. 


Niche.  A square  or  cylindrical  cavity  in  a 
wall  or  other  solid. 

Obelisk.  A tall,  slender  frustum  of  a pyra- 
mid, usually  placed  on  a pedestal.  The  differ- 
ence between  an  obelisk  and  a pyramid,  inde- 
pendent of  the  former  being  only  a portion  of 
the  latter,  is,  that  it  always  has  a small  base  in 
proportion  to  its  height. 

Octastyle.  A building  with  eight  columns  in 
front. 

Ogee,  or  Ogive.  The  same  as  Cyma,  which 
see. 

Order.  An  assemblage  of  parts,  consisting  of 
a base,  shaft,  capital,  architrave,  frieze,  and  cor- 
nice, whose  several  services,  requiring  some  dis- 
tinction in  strength,  have  been  contrived  or  de- 
signed in  five  several  species, — Tuscan,  Doric, 
Ionic,  Corinthian,  and  Composite  ; each  of  which 
has  its  ornaments,  as  well  as  general  fabric,  pro- 
portioned to  its  strength  and  character. 

Ordonnance.  The  arrangement  of  a design 
and  the  disposition  of  its  several  parts. 

Orle.  (Ital.)  A fillet  or  band  under  the 
ovolo  of  the  capital.  Palladio  applies  the  term 
also  to  the  plinth  of  the  base  of  a column  or 
pedestal. 

Ovolo.  A moulding  sometimes  called  a quar- 
ter-round, from  its  profile,  being  the  quadrant  of 
a circle.  When  sculptured  it  is  called  an  Echi- 
nus, which  see. 

Panel.  A thin  board  having  all  its  edges  in- 
serted in  the  groove  of  a surrounding  frame. 

Parapet.  From  the  Italian  parapetto,  breast- 
high.  The  defence  round  a terrace  or  roof  of  a 
building. 

Parastatce.  Pilasters  standing  insulated. 

Pavilion.  A turret  or  small  building  generally 
insulated,  aYid  comprised  beneath  a single  roof. 

Pedestal.  The  substruction  under  a column 
or  wall.  A pedestal  under  a column  consists  of 
three  parts,  — the  base,  the  die,  and  the  cornice  or 
cap. 

Pediment.  The  low  triangular  crowning  or- 
nament of  the  front  of  a building,  or  of  a door, 
window,  or  niche. 

Pend,  (in  Gothic  architecture,)  a vaulted  roof 
without  groining. 

Pendant,  (in  Gothic  architecture,)  a hanging 
ornament  in  highly  enriched  vaulted  roofs. 

Pinnacle,  (in  Gothic  architecture,)  a small 
spire. 

Peripteral.  A term  used  by  the  ancients  to 
express  a building  encompassed  by  columns, 
forming,  as  it  were,  an  aisle  round  the  building. 

Perist.ylium.  In  Greek  and  Roman  houses,  a 
court,  square,  or  cloister. 

Perspective  is  the  science  which  teaches  us 


190 


GLOSSARY  OF  ARCHITECTURAL  TERMS, 


to  dispose  the  lines  and  shades  of  a picture  saas 
to  represent,  on  a plane,  the  image  of  objects  ex- 
actly as  they  appear  in  nature. 

Piazza.  A continued  arch-way,  or  vaulting, 
supported  by  pillars  or  columns  ; a portico. 

Pier.  A solid  between  the  doors  or  the  win- 
dows of  a building.  The  square  or  other  formed 
mass  or  post  to  which  a gate  is  hung. 

Pilaster.  A square  pillar  engaged  in  a wall. 

Pile.  A stake  or  beam  of  timbers,  driven 
firmly  into  the  ground. 

Pillar.  A column  of  irregular  form,  always 
disengaged,  and  always  deviating  from  the  pro- 
portions of  the  orders  ; whence  the  distinction 
between  a pillar  and  a column. 

Platband.  A square  moulding,  wliose  pro- 
jection is  less  than  its  height  or  breadth. 

Plinth.  The  square  solid  under  the  base  of  a 
column,  pedestal,  or  wall. 

Porch.  An  arched  vestibule  at  the  entrance 
of  a church,  or  other  building. 

Portico.  A place  for  walking  under  shelter, 
raised  with  arches  in  the  manner  of  a gallerj"  ; 
the  portico  is  usually  vaulted,  but  has  sometimes 
a flat  soffit  or  ceiling.  This  word  is  also  used  to 
denote  the  projection  before  a church  or  temple 
supported  by  columns. 

Post.  A piece  of  timber  set  erect  in  the 
earth.  Perpendicular  timbers  of  the  wooden 
frame  of  a building. 

Posticum.  The  back  door  of  a temple  ; also, 
the  portico  behind  the  temple. 

Principal  Rafters.  The  two  inclined  timbers 
which  support  the  roof. 

Profile.  The  contour  of  the  different  parts  of 
an  order. 

Projecture.  The  prominence  of  the  mould- 
ings, and  members  beyond  tlie  naked  surface  of 
a column,  wall,  Ac. 

Proscenium.  The  front  part  of  the  stage  of  the 
ancient  theatres,  on  which  the  actors  performed. 

Prostyle.  A building  or  temple  with  columns 
in  front  only. 

Purlins.  Pieces  of  timber  framed  horizon- 
tally from  the  principal  rafters  to  keep  the  com- 
mon rafters  from  sinking  in  the  middle. 

Pycnostyle.  An  intercolumniation  equal  to 
one  diameter  and  a half. 

Pyramid.  A solid  with  a square,  polygonal,  or 
triangular  base,  terminating  in  a point  at  top. 

Quarter- Round.  See  Ovolo  and  Echinus. 

Quatrefoil,  (in  Gothic  architecture,)  an  orna- 
ment in  tracery,  consisting  of  four  segments  of 
circles,  or  cusps,  within  a circle. 

Quirk  Mouldings.  The  convex  part  of  Gre- 
cian mouldings,  when  they  recede  at  the  top, 
formina  a reenticent  angle  with  the  surface  which 
covers  the  moulding. 


Quoins.  The  external  and  internal  angles  of 
buildings  or  of  their  members.  The  comers. 

Radius,  in  geometry,  is  the  semi-diameter  of  a 
circle,  or  a right  line  drawn  from  the  centre  to 
the  circumference  ; in  mechanics,  the  spoke  of  a 
wheel. 

Rails,  in  framing,  the  pieces  that  lie  hori- 
zontal ; and  the  perpendicular  pieces  are  called 
stiles,  in  wainscoting,  &c. 

Raking.  A term  applied  to  mouldings  whose 
arrises  are  inclined  to  the  horizon. 

Relievo,  or  Relief.  The  projecture  of  an 
architectural  ornament. 

Resistance,  in  mechanics,  that  power  which 
acts  in  opposition  to  another,  so  as  to  diminish  or 
destroy  its  effect. 

Reticulated  Work.  That  in  which  the  courses 
are  arranged  in  a net-like  form.  The  stones  are 
square,  and  placed  lozengewise. 

Return.  (Fr.)  The  continuation  of  a mould- 
ing, projection,  &c.,  in  an  opposite  direction,  as 
the  flank  of  a portico,  &c. 

Rib.  (Sax.)  An  arched  piece  of  timber  sus- 
taining the  plaster-work  of  a vault,  &c. 

Ridge.  The  top  of  the  roof  which  rises  to  an 
acute  angle. 

Ring.  A name  sometimes  given  to  the  list, 
cincture,  or  fillet. 

Roman  Order.  Another  name  for  the  Com- 
posite. 

Rose.  The  representation  of  this  flower  is 
carved  in  the  centre  of  each  face  of  the  abacus 
in  the  Corinthian  capital,  and  is  called  the  rose 
of  that  capital. 

Rustic.  The  courses  of  stone  or  brick,  in 
which  the  work  is  jagged  out  into  an  irregular 
surface.  Also,  work  left  rough  without  tool- 
ing. 

Sagging.  The  bending  of  a body  in  the  mid- 
dle bv  its  own  weight,  when  suspended  horizon- 
tally by  each  end. 

Salon.  .4n  apartment  for  state,  or  for  the 
reception  of  paintings,  and  usually  running  up 
through  two  stories  of  the  house.  It  may  be 
square,  oblong,  polygonal,  or  circular. 

Saloon.  (Fr. ) A lofty  hall,  usually  vaulted  at 
the  top,  with  two  stages  of  windows. 

Sash.  The  wooden  frame  which  holds  the 
glass  in  windows. 

Scaffold.  A frame  of  wood  fixed  to  walls,  for 
masons,  plasterers,  &c.,  to  stand  on. 

Scantling.  The  name  of  a piece  of  timber, 
as  of  quartering  for  a partition,  when  under  five 
inches  square,  or  the  rafter,  purlin,  or  pole-plate 
of  a roof. 

Scapus.  The  same  as  Shaft  of  a column, 
which  see. 

Scarf  ng.  The  joining  and  bolting  of  two 


H 


GLOSSARY  OF  ARCHITECTURAL  TERMS. 


191 


pieces  of  timber  together  transversely,  so  that 
the  two  appear  but  as  one. 

Scotia.  The  name  of  a hollowed  moulding, 
principally  used  between  the  tori  of  the  base  of 
columns. 

Sever y,  (in  Gothic  architecture,)  a separate 
portion  of  a building. 

Shaft.  That  part  of  a column  which  is  be- 
tween the  base  and  capital.  It  is  also  called  the 
Fust,  as  well  as  Trunk  of  a column. 

Shank.  A name  given  to  the  two  intersticial 
spaces  between  the  channels  of  the  triglyph  in 
the  Doric  frieze. 

Shooting.  Planing  the  edge  of  a board  straight, 
and  out  of  winding. 

Shoulder.  The  plane,  transverse  to  the  length, 
of  a piece  of  timber  from  which  a tenon  projects. 

Shutters.  The  boards  or  wainscoting  which 
shut  up  the  aperture  of  a window. 

Sill.  The  timber  or  stone  at  the  foot  of  a 
window  or  door ; the  ground  timbers  of  a frame 
which  support  the  posts. 

Skirtings.  The  narrow  boards  which  form  a 
plinth  round  the  margin  of  a floor. 

Socle.  A square  flat  member,  of  greater 
breadth  than  height,  usually  the  same  as  plinth. 

Sojit.  'Phe  ceiling  or  under  side  of  a member 
in  an  order.  It  means,  also,  the  under  side  of  the 
larmier  or  corona  in  a cornice  ; also,  the  under 
side  of  that  part  of  the  architrave  which  does  not 
rest  on  the  columns.  See  also  Lacunar. 

Sommer.  The  lintel  of  a door,  winflow,  &c. ; 
a beam  tenoned  into  a girder,  to  support  the  ends 
of  joists  on  both  sides  of  it. 

Spandrel,  (in  Gothic  architecture,)  the  trian- 
gular space  inclosed  by  one  side  of  an  arch,  and 
two  lines  at  right  angles  to  each  other,  one  hori- 
zontal, and  on  a level  with  the  apex  of  the  arch,  ! 
the  other  perpendicular,  and  a continuation  of 
the  line  of  the  jamb. 

Spiral.  A curve  line  of  a circular  kind,  which 
in  its  progress  recedes  from  its  centre. 

Steps.  The  degrees  in  ascending  a staircase. 

Stereohala,  or  Stylohata.  The  same  as  En- 
tasis. 

Strap.  An  iron  plate,  to  secure  the  junction 
of  two  or  -more  timbers,  into  which  it  is  secured 
by  bolts. 

Stretching  Course.  Bricks  or  stones  laid  in  a 
wall  with  their  longest  dimensions  in  the  hori- 
zontal line. 

Surbase.  The  mouldings  immediately  above 
the  base  of  a room. 

Systyle.  An  intercolumniation  equal  to  two 
diameters. 

Table,  (in  Gothic  architecture,)  any  surface, 
or  flat  member. 


Tceni.  A term  usually  applied  to  the  lastel 
above  the  architrave  in  the  Doric  order. 

Templet.  A mould  used  by  bricklayers  and 
masons  for  cutting  or  setting  the  work  ; a short 
piece  of  timber  sometimes  laid  under  a girder. 

Tenon.  A piece  of  timber  the  thickness  of 
which  is  divided  into  about  three  parts ; the  two 
outside  parts  are  cut  away,  leaving  two  shoulders, 
the  middle  part  projects,  and,  being  fitted  to  a 
mortise,  is  usually  termed  a tenon. 

Terrace  Roofs.  Roofs  which  are  flat  at  the 
top. 

Tetrastyle.  A building  having  four  columns 
in  front. 

Torus.  A moulding  of  semicircular  profile, 
used  in  the  bases  of  columns. 

Tracery,  (in  Gothic  architecture,)  a term  for 
the  intersection,  in  various  forms,  of  the  mullions 
in  the  head  of  a window  or  screen. 

Transom,  (in  Gothic  arcliilecture,)  a cross 
mullion  in  a window. 

Trefoil,  (in  Gothic  architecture,)  an  ornament, 
consisting  of  three  cusps  in  a circle. 

Triglyph.  The  ornament  of  the  frieze  in  the 
Doric  order,  consisting  of  two  whole  and  two 
half  channels,  sunk  triangularly  on  the  plan. 

Trimens.  Pieces  of  timber  framed  at  right 
angles  with  the  joints  against  the  wall,  for  chim- 
neys, and  well-holes  for  stairs. 

Trimmer.  A small  beam,  into  which  are 
framed  the  ends  of  several  joists.  The  two  joists 
into  which  each  end  of  the  trimmer  is  framed  are 
called  trimming-joists. 

Trough  Gutter.  A gutter  below  the  dripping 
eaves,  to  convey  the  water  to  the  pipe  by  which 
it  is  discharged. 

Trunk.  See  Shaft.  When  the  word  is  ap- 
plied to  a pedestal  it  signifies  the  dado  or  die,  or 
body  of  the  pedestal  answering  to  the  shaft  of 
the  column. 

Truss.  When  the  girders  are  very  long,  or 
the  weight  the  floors  are  destined  to  support  is 
very  considerable,  they  are  trussed. 

Tuscan.  One  of  the  orders  of  architecture. 

Tusk.  A bevel  shoulder,  made  above  a tenon, 
to  strengthen  it. 

Tympanum.  The  space  inclosed  by  the  cor- 
nice of  the  sloping  sides  of  a pediment,  and  the 
level  fillet  of  the  corona. 

Vault.  An  arched  roof  so  contrived  that  the 
stones  or  other  materials  of  which  it  is  composed 
support  and  keep  each  other  in  their  places. 

Vestibule.  An  ante-hall,  lobby,  or  porch. 

Vice,  (in  Gothic  architecture,)  a spiral  stair- 
case. 

Volute.  The  scroll  which  is  appended  to 
the  capital  of  the  Ionic  order. 


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